Even if you find this part, older Onan gennies can be troublesome, particularly if they have not been used much. It could be quite tasking to get it to run smoothly since their carbs tend to gum up easily, some have luck cleaning them, most times a new one has to be ordered.
Portable gennies is another route to take, inverter versions run quieter, provide cleaner power, and are more fuel efficient. We have a Champion 3K watt inverter genny with electric and remote start, easily powers our single AC unit and most 120Vac items on our 30 amp rig at the same time.
Being new to RVing do you plan to have power hookups most of the time, or is your preferred method primarily off the power grid? Two (or 4) house batteries will better serve your needs for off grid camping, we use 6 volt GC2 batteries from Samsclub, a single 12 volt can work if mostly using electric sites.
Our last 3 RVs have had onboard gennies, our first 2 TT/5er did not and we did not purchase a portable genny, that was 2 decades ago & did not realize their benefits when RVing off the power grid. Although we have solar we quickly learned that our Onan provided 100% self-containment at a touch of a button.
