My question is do they have generators to fit your 50amp prongs?
To answer your question yes they do. My Kawasaki 5000 has one. As far as getting one for a back up however, I doubt you will need or want one that big. You will be told you need everything from a 2000 to a pair of 2000's to the 5000 so I won't help confuse you.
2008 Dodge Ram 6.7 Laramie SRW SB
2012 Keystone Passport 26BHWE
2009 Lance 830 with Tent foldout
20' North River Seahawk Boat
2005 Honda VTX1300
Most people don't have a backup Gen for their house. Why would you need one for an RV? Just one more thing to maintain.
While that may be true, every year that a hurricane even brushes the coast of Florida, there's a run on generators. Seems to be a prevailing thought that it's better to have it and not need it than to need it and not have it.
Then there's the fact that nearly all Class A's rolling down the road, and probably most Class C's, have an on-board gen-set. I've even seen 5er's with built-in generators. Heck! I have an on-board generator in my truck camper. So, I'm not dependent upon a camp ground with electric, whether it's summer in the southeast or winter in the north. I've worked in both areas for days in which power was out due to storms or not available due to the time of year.
Camping styles vary as much as the people who are engaged in it. If you can perceive of a time when a genny will come in handy, get one. If not, I wouldn't worry about it.
All I can tell you is when I was dodging 4 hurricanes in Florida in 04, or got stuck in Buffalo's "October Surprise" in 06, or Hurricane Ike's damage in Ohio in 08 amongst other situations, I sure was glad to have a generator. Because, there wasn't any power where I was for a number of days. I didn't miss a beat. Was cool in the heat and warm in the cold. Watched satellite tv as much as I wanted. Made coffee for the neighbors and linemen working on the poles. To each, his own
My suggestion: I'd go for a 6000 watt model from Honda or Yamaha (ef6300iSDE for Yammy, eu6500is for Honda), and call it done. You won't be able to get two full 50A legs from this, but you will be able to get 45-50 amps, good enough to run two A/Cs.
As an alternative, a lot of fifth wheels have a generator-prepped compartment. It might be possible to have a pro at electricity and LP gas route piping and install an onboard Onan with a transfer switch.