https://www.amazon.co.uk/gp/product/B07S4HF3J2/Lead's going a bit far. I got these when I realised they'll be using this virus as an excuse to track us ever more. Obviously test the product before going out there. Literal tinfoil would do, it looks like, if you really want to do it yourself.
A lead-lined box is great for protecting circuitry in that mythical but much-feared event, an EMP attack, so why not make one to safeguard a copy of your money on a stick drive, in case of incomplete information and other surprises. Also handy for clonking people on the head.
You'll still have to pull it out to use it.
They then can only say you used it that once, without breaking their cover. Depends how untidy things get how much this matters.