If you have bay space for a built-in generator, either Onan or Generac will work for you. I have a Generac in my motorhome and did have a problem finding an "Authorized Generac" repair facility. I did find one, but it was a heavy equipment company and my MH looked kinda out of place in there next to all that equipment. But I did get it repaired and haven't had any problems since.
However, I would recommend you get a small portable generator. That way you can set it up either at the back of your trailer or, if you want some peace and quiet, all the way out at the end of your power cord. Honda makes some good (but very expensive) small generators and Ken at Grandview Trailer Supply carries a comparable (but not so expensive) brand. Either way you go, built-in or portable, just make sure you buy one big enough to run whatever electrical appliances you need to run.