I don't carry mine in my wallet*, but I do what I consider to be a viable alternative. I keep all of my C-Cards (and my DAN Insurance card) in a "Passport Folder" in my reg bag. The odds of me going on a dive trip without my reg bag are infinitesimal. (I don't dive locally.) Once I get to my destination, I will secure them with my passport & plane tickets till I head home.
*I do carry a spare AOW card in my wallet though because once I thought I had misplaced my cards and I ordered a replacement AOW card to "get me air" while on a dive trip. (I found my cards about 5 minutes after I had ordered the replacement card but by then, PADI had already charged my credit card and confirmed the order.)