Arrival
(I don't own the Flash or the Harry Potter franchise and make no profit)
Harry woke up gasping for breath and clutching his chest trying to get himself calmed down enough to remember why he was on the cold hard ground in a cavern of some sort, realizing that panicking would help no one here he started to take deep breaths. After he got his breathing calmed down he reviewed his memories with help from his occlumency he reviewed the situation he was in now.
He broke from his musings by the coughing of a throat. As he tensed he slowly turned around to find a hispanic woman inspecting him with a critical eye "Hello?" Harry asks the woman across from him breaking her inspection of him. "Harry Potter?" She asks. Alarmed that she knew who he was right away he slowly says yes and asks who she is. She replies her name is Ersin Fortuna an immortal on this Earth. That only makes him more wary of her but she explains that in this universe he is a fictional character in a book which looks like the first in a series.
After speaking with her for a while he got the information on where to take his gold and get a new identity for this world. His first stop is a shady building not to far from the Casino which he exited as he entered it was barred up and obviously not well taken care of but would suit his needs for the moment. After meeting the owner a short unremarkable man and haggling for the price of the gold around a tenth of his vaults he left the store 50,000 US dollars just enough to have a great new ID made for him that would pass any scrutiny that he would face with a believable background. The next issue was how to find such a person that would do so.
Over the next month hanging around in shady areas and talking to people he would regularly avoid he got a tip to head over to Starling City in search of a man called the Calculator that had disappeared under the watch of the FBI. Arriving in the central part of the city (through disapparition he is on a budget after all) he took out the death stick and cast an overpowered point me spell to the calculator and saw that he needed to go to the south. With a series of apparitions only around two blocks each time and recasting the spell between it took around seven hours before his wand changed direction pointing back to his previous direction. By this point he was far removed from the city and quite tired so he saved the spot in his mind and found the nearest hotel booked a room with a quick confundus charm and got a nights rest.
The next morning after a shower and proper meal he transfigured a good looking suit that didn't appear too new nor did it appear too old, after all it is best to not look like he cannot afford the ID nor it is good to show great wealth to avoid getting ripped off. Following his inspection he apparated back to his location from the previous evening and checked the point me spell one more time to make sure that he was on the right path. After the spell confirmed that he was still there Harry began walking to the door. Knocking on the door it was evident that the Calculator was not expecting company be the newly found silence knowing that if he says the wrong thing it will end his chances with this man he carefully says, "Hello, I'm having some financial problems and find myself in need of a calculator." Hoping that it was subtle enough for the man but not incriminating enough that the man would run. After waiting a few breaths he could hear the sounds of a man walking to the door. Putting on the look of a man that looks like he is trying to hide his desperation on his face he stands wringing his hands after a few moments the door starts to slowly open and Harry sees the unassuming man but inside his eyes he could see the intelligence and the calcutalive gleam (no pun intended) they both assessed each other for a few seconds as Harry moved to speak the Calculator broke the silence first telling him to come in.
"Tell me, what is it you need?" he asks casually. "I found that I had lost all of my identification paperwork and need the whole package" Harry replies. "Hum, the whole package? Do you have enough money for such a problem?" Once again no influx in his voice just the same monotone. Slightly annoyed Harry answers, "Yes the whole package, and I should have enough." After a few security questions he is seemingly happy with the responses he says tells Harry that the package will be finished in one week and to go to Starling City at the Queen Industrial Inc. and to pay half the fee now and half to be delivered just after delivery of his paperwork. The only decisions that were needed right now were his new name what school he went to and his scores in classes that he went to in the school. He decided that his new name would be Sirius Evans to honor his godfather and his mother and to keep his middle name the same, for his school he said to pick a public school in the city that would be overpopulated so it would make sense that no one would remember him, and finally his grades were good enough to get into most colleges but not for someone to take keep up the ruse Harry tried to haggle the price down in the end it was decided that right now Harry would pay twenty thousand up front and twenty thousand upon delivery making the total forty thousand dollars. A good portion of the money that he already had but enough that he could still afford the total cost and find a good hotel to pay for this time.
One week later he was forty thousand dollars poorer and the world has now found the rise of Sirius James Evans.
Sorry about the wait was deciding how to take the story, if any meta powers, what they would be, and of course my chronic procrastination but I have decided on all but one how to proceed from here. Also when he didn't find the JLA members it was a quick search and Barry didn't even find them with years of searching for people with powers.