If you are looking for a low cost USB key that support OTP, then SafePass is the ideal choice. SafePass is a FIDO/U2F key that supports both OATH/HOTP and OATH/TOTP.
Specification
| Function | OATH/HOTP,OATH/TOTP FIDO/U2F |
| Size | 43.9×20.8×3.1(mm) |
| Weight | 2.7(g) |
