We're pretty lucky in the sense that we have a member who runs a print store and so has the whole plastic credit card setup. In fact, he uses those as his tags that he attaches to his kegs.
One thing we do, just for CYA purposes, is the back of the card is also printed with a disclaimer about consumption and being an idiot. I have no clue if it has any standing legally, but it's there as a good reminder to folks - don't be a dummy, dummy.