Originally Posted by
NotSoMechanic
Yeah, it's unfortunate. I don't like when things become obsolete via the market. I did find a nice set of shimano sora for 9 speed on ebay.
I wonder if it would be worth replacing the cassette? But that is a lot more effort than I think he or I are committed to

To Replace Cassette and chain you would need a new derailleur as well as new shifters assuming we are talking about an upgrade in speeds. 9 speed was the last bastion of road and mountain working together and everything being easy to deal with once we hit 10 and 11 things splintered off so the older tech isn't going to work very well and the new tech has to match up.
Keep in mind the Shimano Heirarchy for their road group sets from the bottom of the dumpster on up is Tourney, Claris, Sora, Tiagra, 105, Ultegra and Dura Ace at the top and for Mountain Bikes it is Tourney, Altus, Acera, Alivio, Deore, SLX, Deore XT, XTR and at the top.