I have multiple suggestions for you.
1) check out a
Party Pig store, or any
party supply store. Go to the
Pirate Party theme section. There you will find bags of gold dubloons. They might also be in the Mardi-Gras section.
2) check out a
teacher supply store. I went to one called Teacher Heaven here in Austin, and they had some very cool looking gold goins (which I bought them out of) that looked very accurate. But they also had plastic coins. They had bags of plastic nickles, dimes quarter, dollars, half dollars, pennies and silver dollars. Plastic Sacajawea dollars. They had coins from several different manufacturers and combination kits that would work ideally for low level campaigns where you use copper, silver and gold coins.
3) Use
Shrinky Dinks. Find some pictures of cool looking coins on the internet, and cut and paste them into a word document. Or just draw them out inside circles on a sheet of paper. You will have to make them bigger because they will shrink when you bake them. Then cut them out (you definitely want to cut them out first). You can even use a yellow marker to color them an appropriate color. Then you bake them following the directions and they shrink and thicken and become very durable hard plastic coins to your own exacting specifications.
4) Use monopoly money. If you don't have any, you can print your own. Check out this link here:
http://www.hasbro.com/monopoly/pl/page.treasurechest/dn/default.cfm
5) Use Fantasy Money availabe at this link here:
http://shop.enworld.org/index.php?productsid=1855&source=frontpagead
6) Make your own "paper" gold money with clipart or drawing it yourself. Attached is one I did and which I use in my game. Print different denominations out on different colored paper. Go to an office supply store and buy a pack of colored paper.
I use red paper for copper coins, grey for silver, plastic gold dubloons for gold pieces, light blue paper for platinum, goldenrod for 100 gold bills, and green for 1000 gold piece bills which will become handy at higher levels. Honestly the color coding is practically essential to make them handy for quick transactions in a game, so go to the slight expense of using colored paper if you are going to to do this. We use this money exclusively to track wealth in my home campaign.