I don't know anything about URC remotes, but the manufacturer says that if you have the latest software, you can enter IR codes in Pronto Hex format. We can tell you the Pronto Hex for any function of your receiver.

Yamaha receivers have for years used the NEC1 IR protocol, using device 122 and more recently 126. The RX-V371 uses a variant of the NEC1 IR protocol for most of its discrete commands, and few universals have this variant built in.

If you can't get Pronto Hex into your MX-900, then you could buy the cheapest Harmony and teach the commands. If the Harmony is missing any commands, (likely) then you can send the Pronto Hex to Logitech, and they will eventually add the commands to your Harmony. I think this can only be done for new Harmony remotes within a few weeks of purchase.

Or you can get an e.g. RCA RCRP05B (or many cable company remotes) and a JP1.3 cable and again teach your MX-900. No expiration date on this method.