I'd imagine you could just wrap your card in aluminum foil (like from the kitchen) if you don't use it very often.

That could work, but is cumbersome (there's a post about convenience here somewhere). Most wallets that look like a billfold, should be easy enough to modify with a piece of tinfoil in the bill section, which encloses most of the wallet when it's closed. I think some testing of this might be in order...