[ericseppanen]

A Solo key is $20.

https://solokeys.com/

[CameronNemo]

Note that the feature set on this is limited. Specifically it is missing GPG (and thus SSH) support. It may be added via a software update if the somu campaign goes very well. But frankly that is a long shot.

https://www.crowdsupply.com/solokeys/somu

Of course if you only need WebAuthn then solo keys are a great option.