NostrGram.co shows you the relays. Login, search for the note ID and click the information icon in the upper right corner. At the bottom of the event structure it shows the relay list.

astral, nostr rocks, a handful of og clients had guis for this and if you click on the not seen on button it would broadcast specifically to that relay, pleb facing clients don’t want end users to have to think about this but I’d love to control where I’m broadcasting and rebroadcasting too.