I have these and they do work.
2 X Car Key Signal Blocker Case, Faraday Bag for Car Keys Keyless Entry Fob Guard RFID Signal Blocking Pouch Bag, keyless car key signal blocker pouch, Cell Phone Protection RFID/ WIFI/ NFC Blocker
https://www.amazon.co.uk/dp/B076KZF6..._-B-2Cb3V7XHHN