Also can be found at the luggage-tag-guy in Itaewon (Seoul, S Korea)...had one that I used for a few years, but then zip-lock bags work fine as well!!

BTW, don't save the coins we all pick up all over the world...I hang on to them till I DH on EK, CX, etc (or stay at a Sheraton somewhere) and donate the coins...Also, recently donated a bunch on both Etihad and Turkish Airlines...