After our built in Onan died, I bought two Honda 2000i portable generators for a lot less than a new Onan would cost. I find the portables are a lot more flexible to use than the built-in. I've used them at home when the power went out, at a buddies remote cabin construction, for work when we needed power at a remote site and of course for the 5th wheel. I carry both if we will need to run the air conditioner or just one if no air conditioner will be needed.
I find we can run them all weekend on about 7 gallons of gas.
If I was buying today, I would buy a Honda 3000 with a remote start setup (you can get them online).