I sometimes find Advil and Tylenol in small cases that are bit smaller than a shot shell and come with ten of either and a lot of empty space. Walmart also has small bottles of both in their housebrand that come with 50 tablets in a 1" diameter x 1.25-ish tall, that you can add about 40-50 more to.
The small altoids tins work (not the standard, "PSK" size). I use the little tubes as well - 10 packs of Advil, Tylenol, etc. Concievably, empty chapstick tubes. Tic-tac containers.