Replacement coins for At The Gates of Loyang
A friend of mine got some Mexico pesos.  They seem to work fairly good, and are fairly heavy.  Different sizes as well.  How you get them if you don't have a friend traveling there, I'm not sure.  But I wouldn't be surprised if they aren't a cheap option for metal money.

http://coins.about.com/od/worldcoins/ig/World-Coins-Gallery-Index/Mexico-Money---Coins.htm