Sherlock's already promised to himself that he's going to do everything in his power to give John a happy Christmas. He'd acquiesced to the decorations, and he's been downstairs getting tips from Mrs. Hudson on how to prepare the perfect Christmas dinner. He'd debated a goose but thought that might be overkill, and instead settled on a standard turkey.
One thing he's missing, though, is a decent gift. He wants to get John something the doctor will use and appreciate, but perhaps a bit more elegant than what he's used to. He walks into the shop, cringing slightly at the flashing lights and tinny music as he's assaulted by an overly-cheerful clerk.
"Happy holidays, sir! I bet you're looking for a gift for that special someone! Would she like some jewellery, or perfume?"
He gives the woman at the counter one of his patented put-on smiles, charisma dripping off him even as he bites back the frustration at her inanity building up inside him.
"I think he" he emphasizes the word clearly "would like a nice jumper." He holds up one he found on the shelf. "Would you have something similar to this in a soft blue?" Sherlock sighs. John had better appreciate the lengths he's going to for this. "Something luxurious but also relatively sensible, maybe in a cashmere-wool blend."