FairWitness
Student
One options is to keep your eye on eBay coin lots. A few years ago I found someone selling bundles of old 100 yen coins, something like 20 of them for $16. Over time I managed to get quite a bit of 100 yen coins this way. Even tho it's paying a premium for what I'm using it for, I like it mainly for a sort of authentic experience of dropping 100 yen coins in the slot, etc. also no modifications required to the coin mechs on my cabs.