Northern tool sells them:
NorthStar PTO Generator 7200 Watt, 14 HP Required | PTO Generators| Northern Tool + Equipment
Messicks sells a package deal on a trailer & the powerhead is AVR regulated. You don't really need a trailer, just a 3 point carry all type set up works fine:
Tiger Power PTO Generators
I have a Winco 24KW. My 40 horse tractor runs it to capacity @ 2,000rpm which equates to a gallon an hr. But keep in mind this will run the whole house...everything. Most folks don't run a generator 24/7 and any time I have had to use one for a week or so I run it about 8 hrs a day. I have a 300 gallon diesel tank, so re-fueling is not a big deal. A tractor is designed to run long hard hours day after day. Heck it takes tons more abuse when cutting, teddering. raking and baling hay.
I have a small 3600 Boily Pro that I use for camping & small jobs on the farm. It's a very well done knock off of the Yamaha but for less than half the price.
New Boliy Pro3600SIE Inverter Generator with Electric Start - Free shipping (click here to order)
I think Honda makes the best portable generator on the market so I don't think you can go wrong with one. Keep in mind that if the insidious ETHANOL makes it's way into any small engine carb, then sits for over a month or two it's going to rein havoc. I recommend Marine Stabil on all small engines or ethanol free fuel which is getting harder to find in some states.