Enamel pins / acrylic figure keychains are very popular item in the fan art / artist alleys at anime/comic conventions, with many companies offering prepress help ( off my head I recall zapcreatives doing acylic and wood for keychain/charms ). Both are things that can be made bulk ( the more you buy in an order the cheaper they all are, 2-6$ish) and are popular collectables usually marked at 10-15$ per pin/charm (pending complexity and size.)
There's been a bunch of Kickstarters since October with lots of beautiful custom designs from artists, too, to get ideas of the breadth of the possibilities ( often kickstarters get the most of the pins, and then overflow is sold through their private websites or etsy shop. )