Thank you both for the ideas. But I should have predicted what's happened:
I'm in Pt. Charlotte, FL right now, aka Bumfuck Egypt, aka Redneck Swamp trailer park hell. So sure enough, every place I went asking for Keen and Camper I got blank stares and "never heard of it"s. Gee, what a shock! Finally, i met a woman from England working in one of the cheeseball mall stores. She said she knows of a place that sells Camper in NY but noplace around here. Again: shocking!
Yes, i know you can buy them online but I can't bc I have no credit cards and I'm leaving in 2 days anyway. So apparently i'll just have to buy them when i get to London.