If you want to borrow coins in your environment, my suggestion would be to concentrate on effects that do not require a gaff.
Thanks for your help. But.... here's the second part of the Australian Coin Magic problem.
Down here, it's illegal to deface any form of currency, and the fines are quite hefty. This means it's virtually impossible to acquire Cig Thru Coin, Folding Coin, Double Sided, etc. in local currency.
Occasionally you'll find a friend of a friend who knows somebody whose willing to have a go at making a gaff, but let's just say that more often than not, the end result is less than perfect.
So... to do any of the above mentioned routines involves ringing in an American coin and trying to explain why you couldn't do the trick with a borrowed coin.
I guess it's quite a similiar situation to bringing out a packet trick during a set of card effects, the difference being that you'll generally have trouble borrowing a deck of cards from an audience member.
I've always felt that coin magic loses quite a bit of wonder if the coins are not borrowed. Nearly everyone watching will be carrying coins of some sort, and they're quite right in wondering why the magician doesn't perform these miracles with 'normal' coins.
Just something to ponder... ;)