I just found this, and love the idea (especially if @Slayer1551 makes one where the card can slot in the back of Hot Chip!)
https://community.monzo.com/t/hot-chip-3d-print-orders/16782
Example from @Avidfanofstuff
https://sjc3.discourse-cdn.com/business5/uploads/monzo/optimized/2X/c/c3a0c07a68ef75294ce35bbfc355743d734425ee_1_375x500.JPG
https://sjc3.discourse-cdn.com/business5/uploads/monzo/optimized/2X/2/210ef1dec7f4167232f44c7aa96c6563d75d2927_1_375x500.JPG