You can build yourself, yes if you are really dedicated to it, it's open source from software to hardware (schematics, BOM -- all of it): https://github.com/keycard-tech/

Second, it's more secure because keys stay on the Keycard's secure element, even during signing.

Since keys stay on the card, you can use unlimited Keycards with any Shell - for multiple seeds, or encrypted backup cards.

Shell also has a Duress PIN. Works airgapped without usb cable (other than charging). Works via QR with most big wallets: UniSat, BlueWallet, Sparrow, BackPack, imToken & 10+ more via BC UR and ERC-4527. And replaceable Nokia BL-4C battery.