Looking for 9 Speed Derailleur

My rear derailleur is almost due for replacement, it’s developed slop over the years. It’s a Deore XT RDM-772 from 2009. The bike is a 2009 model, and I’ve considering upgrading to a 10, 11, or 12 speed setup, but the cassette, chain, and shifters are all fine. I can get an Alivio 9 speed replacement, but would rather stay at the same level or higher. Anyone have an older 9 speed XT or XTR that is still serviceable they would sell?