Paddy, Thanks, I'm so going to steal that idea. And save $4 by cutting a scrap off the roll I have and using clear packing tape.
Okay. I'm back now. While 6.5" long would work for US currency, for a half length to hold credit cards and driver's license, the entire length needed to be 7.5". I did one full-length pocket for currency (somewhat deeper than strictly needed) and one shallower, half-length pocket for cards. Additional organizer pockets for business cards, etc, wouldn't add much weight.
Results: 3.5 grams. Versus 50 grams for my leather wallet and I tend to buy minimal wallets. And Tyvek is infinitely more waterproof than leather.
Even smaller and lighter would be just a credit-card-sized Tyvek pocket with currency folded to fit.
PM me with your snail mail address if you want me to send you a 20" strip of Tyvek. You're on your own for the packaging tape. I recommend name-brand (3M-Scotch) tape - some of the off-brand stuff tears too easily.
For fishing, I need DL, fishing license, CC, and gas money. I've been tucking that all in a zip-lock, but this Tyvek wallet would work better. For BPing, I'd go with the CC-sized Tyvek pocket, maybe with a tapered flap that doubles back through two slits in the body to close it up.
The other thing I'll use it for is Italy next month. No shortage of pickpockets in Rome and to have a "throw-away" wallet with gelato money and a subway card in it is what I'll handle in public and have in my back pocket. A second wallet with more money, ID, etc, will be tucked in my skivvies (so waterproof is good).
I'll post pics from my phone.