Yubico currently sells one at $20. https://www.yubico.com/product/security-key-by-yubico/#security-key-2-pack https://www.yubico.com/product/security-key-by-yub

Yubico currently sells one at $20. https://www.yubico.com/product/security-key-by-yubico/#security-key-2-pack https://www.yubico.com/product/security-key-by-yubico/#secur... There are competing U2F keys, but I don't know of any competitors that support FIDO2 yet.