I thought of this as well, but it only reduces the exposure (like the rf blocking sleeve). When the tag is activated by the reader that's a signal for a skimmer to read it a second time. The electrical contact interface is much more secure than rfid. Even QR-code is more secure. The simpler, less gimmicky method is just to print some business cards with a single-use lnurl-pay qr code. Just hand the cashier the card and they throw it away after using it.