I don't understand the nostr context, but why can't you use a deterministic nonce generation algorithm? (Unless you're doing musig in which case, yes, you basically can't). Either the bip340 suggestion, without injecting fresh randomness, or rfc6979 even?

Not being rfc6979 shouldn't be a problem, the algorithm is never a matter of consensus with other parties.

Doubtless I missed at least one thing here ...