If I remember correctly, you can actually order any coin size, and simply expand the internal slot. Hard to explain, but if you look closely at the photo at the top of this thread, the 25c slot has a little 'restriction' at the top of the coin entry. If that restriction is fully cut out, the outer entry size is perfect for a 20c coin.
The size out the outer slot is size for a Aussie 20c coin, and they are then varied for each smaller coin by the size of that secondary restriction.
...The hard part is, where do you get a red/black decal for 20c coins?