Amethyst or Nostrudel will show you what relays it's coming through on.
My relay wss://n.ok0.org was also hit by this asshole a few days ago. I've evolved the write policy to capture his shit so I've managed to get rid of him for now.
Spam like this is very tricky to weed out on Nostr, this guy is creating a new key for each message so banning npubs is useless. The text is always random and he changes the URLs he uses, so you have to get creative on how you catch it, without throwing the baby out with the bath water.
These bots are probably spamming that on any free relays they can, I doubt many of them will be able to filter it. Anyway, you are welcome to use wss://n.ok0.org
Spam will happen here too, but I do keep an eye on it and change the write policy to catch it where possible.