What about a bra?

You start pulling the clothes on, starting with the underwear that looked far too much like bloomers, and then pull on the sweatpants. You're about to pull the sweatshirt over your head when you realize that Alex never handed you a bra. You call out through the door to him, "Don't you have any bras?"

"Yeah, but I don't know what your size is." For that matter, neither do you. You look back at yourself in Alex's mirror, and try to guess what size your chest might be. They look like Cs, maybe? Or possibly Bs? Or Ds? You have no idea, honestly.

"I think I'm a C?" you call back, unsure.

"Are you sure?" comes Alex's reply. "I can come check them out for you, if you need me to."

"Fuck off! Just tell me where the bras are!"

Alex concedes, and tells you where to look. Now you just have to find one that fits you.