I appreciate that this response won't answer your question, but rather than using an RFID-blocking wallet, I carry a
Vault Card inside my wallet.
So far I have tested this by trying to "tap-in" and out of train/tube stations in London, and by trying to open doors in the building where I work. The Vault Card seems to do the trick, because neither of these systems work unless I take the appropriate card out of my wallet.
At least this method allows you to carry on using your existing wallet, rather than replacing it.