At some point, I got the impression that the phrase "fag bag" refers to the old "fanny packs" that were all the rage some years ago. In the U.S., it seemed like everyone was wearing one of those narrow zippered packs around their waist. I think I first heard "fag bag" when I took a road trip with my friends from L.A. to Florida (I wish I had my empeg back then) and encountered the running joke that only gay residents of southern Florida wore those things.