Lisp jobs are sometimes advertised in Who's Hiring threads, Reddit's r/lisp, etc. There's a Lisp job advertised on Reddit [1,2] right now even. Another good source is to check out the companies in [3] and see if they have any openings on their website (or cold-emailing).

[1] https://www.reddit.com/r/ProgrammingLanguages/s/AZmouaoARl

[2] https://jobs.lever.co/dodmg/af802f7f-4e44-4457-9e49-14bc47bd...

[3] https://github.com/azzamsa/awesome-lisp-companies