I've been using this type (brand) of wallet for about 6 years. When I found this particular wallet, I decided to add some RFID shielding to it using Aluminum tape. This tape is used for sealing heating ducts as it is more durable than cloth based "duct" tapes.
NOTE, my first one of these wallets lasted four years, I'm on my second one now and I expect it to last about the same amount of time.
No endorsement is intended or implied, I paid for all the materials that I used.
Step 1: Materials and Tools Needed
A Tyvek wallet, Aluminum duct tape, a pair of scissors and a marker.
Step 2: Measure Out Tape
Roll out the tape, lay the open wallet on it and measure and mark the length. Cut it and measure out three more pieces.
Step 3: Open Up the Wallet
The wallet just fits together with folded in pieces and is very easy to open. The only piece that is stuck together are the card slots. this part doesn't need to be taken apart.
Pictured is the wallet opened up.
Step 4: Assembly
Peel the paper backing off one of the pieces of tape. Line it up with the top edge of the inside of the back of the wallet and stick it down, and smooth it out, remove the paper off of a second piece, line it up with the bottom edge of the back of the wallet and stick it down. The last picture is what it should look like.
Step 5: Second Piece of Shielding
Take the next two pieces of tape, line them up overlapping so that they're the width of the wallet. Mark the tape and lift the paper backing up to where it has been marked, line up the two pieces of tape and stick them together.
Then slide this piece of tape into the middle slot of the wallet, as pictured.
Step 6: Reassembly
Reassemble the wallet and fold it for normal use.
Step 7: The Completed Wallet
The wallet is now done and is only slightly thicker then when you started.