There wouldn't be a large number of parts in common with the holdens.
Importing parts from overseas really is the best option. They are plentiful, and postage isn't that expensive.
If you buy from an organised vendor, they will usually arrive in around a week, possibly less.
You can get parts locally but they tend to be more expensive as their stock generally comes from overseas, so they have the purchase price, shipping, storage and overheads before they add their mark-up, GST and possibly shipping to your door.
I have bought heaps of parts from overseas for a number of different cars fron a few different countries and have never had an issue, ranging from $10-20 purchases to a bit over $5000 for a 5-speed manual conversion for my vette. Just make sure you buy from a reputable company and you're fine.
The few times there was a problem, it was sorted quickly and easily. I have had more problems from Australian ebay shops than US car parts shops.
ps. I wish I had a C2 :tear: