I've been trolling thrift stores all summer here and the two brands I most commonly see are Certainty Fitted Briefs (bleh.) and Tranquility ATN (yay!). But the ATNs are ALWAYS Extra Small (or Small in the new sizing scale). I've never seen a Medium or Large. I get more and more grumpy that all they ever have is XS. :P
Any clues as to why that is? Is it just that the medium/larges get snapped up right away? Noticed the same thing in shoes, by the way. I've been looking for some patent leather dress shoes for Commandery drill. All of the ones I've found in my size have been trashed beyond restoration and the ones that are nice are all too big or too small.