Fwiw big players regularly give free keys to e.g. OSS maintainers. Dunno if it’s still active but Pypy has a program for maintainers of crates flagged as sensitive (or something like that), you can get two Titan keys courtesy of google.

I also have a pair of github-branded yubikeys from a long time ago but I don’t remember what that program was.

> cost has been prohibitive.

A titan is 35 or so, hardly prohibitive. And if you have access to anything important your company ought be glad to get you one or two, or yubis.