Walk Behind Lawn Mowers

I bought a used Husqvarna HU775L 961450008 self propelled lawn mower. I need a replacement drive belt and cannot find the replacement belt number. I have the manual and it does not list it and I have searched the internet and can find every other model, but not the HU775L belt. Can you tell me what belt I need?
thank you
Darcy Cawley