I'm a T-Shirt junkie, so if you had a wide selection of just common Foundation stuff, like memes or popular SCPs, or even just the symbol or something, at a moderate price, I'd probably pick up a few to start with and then maybe like one every couple of months. A couple ideas: I think someone mentioned a 'I survived Procedure 110-Montauk shirt, and I would totally buy a shirt that was just literally the SCP-173 page.
I agree with you on the lab coat, but I'm not sure how well that would do in sales, because it's not normal wear and oddly… specific.
I too would like a tiny model 682 to place and my desk and a 173 statue to keep from falling asleep while doing school work.
I think a black/white baseball cap with just a white/black foundation symbol would be pretty sick as well.
Maybe a tin full of tic-tac like mints that look like SCP-500?