They also operate out of New York.

Gandi appears to still allow registration of them: https://www.gandi.net/en/domain/tld/su.

I didn't actually register one, but they quoted a price of $28.31 for the first year then $63.98/year afterwards.

Technically that's not even the official site for the .su tld, it's for a registrar that operates out of the US, but there are many.

https://www.iana.org/domains/root/db/su.html