Here’s a link to a post that I put up a while back. The material I used is polyester based, prints well (laser printer only), and is very waterproof. I use it for printed car decals. Drawbacks are that it is only letter sized and requires a laser printer.
If you have access to a laser printer and can live with the size limitations, I highly recommend this material. It rivals game pieces I have gotten in other commercial games and will be much more durable than paper. If you’d like to PM me with your address, I can mail you a sample item and a piece of the material.