Suggestions off the top of my head:

* Specifically mention that you're after someone with nontrivial open source experience/maintenance experience and you'll accept it in place of Leetcode

* Some inkling that you've thought about titles/HR considers "maintainer" as experience

* Provide the expected time commitments from interviews upfront. Likewise for compensation.

* Expect part-time or contract work. If full-time, explicitly allocate time to their OSS.

* Remote, if part-time or contracting

* Async friendly. I've had 1 "real-time" meeting in OSS (total).

* Post a spec/contact details in a reply to this comment, or "Who is Hiring"

Send them a mail offering funding, asking their preferred payment method and then send them money every month until they stop maintaining the software.