There are about 8 of them now that I'm aware of. Once you add the relay, make sure that you check the read and write boxes or toggles, then go and pay for it. Once your invoice is paid, your public key is added to the whitelist database and you're all set.

I'm using:

wss://eden.nostr.land

wss://nostr.milou.lol

wss://nostr.orangepill.dev

wss://nostr-pub.semisol.dev

I may look into more in the coming days as more people move over to paid ones.