Bob,  The parallel kits are pretty common for the Honda dn Yamha invertor type generators.  Most of the place where you would buy those generators sell the kits. But I've seen instructions on how to build the cable someplace  my web surfing..  Probably on RVnet.  Google and see if you can find it.  A man of your talents would have no problem assembling the few parts needed to build the connector and you would save a bunch of money over what Honda charges

To the original poster.   Most A/C units on horse trailers require 1800 watts to run. But often need a little over 2000 to start up. So the minimum reccomendation is usually a generator that produces at least 2000 continous watts and might have a burst mode slightly higher. I had heard that a single Honda 2000 was not strong enough for the start up load on most A/C units.  So you would need the parallel set up using dual generators to get the A/C started and running. I bought the Yamaha EF2400is that had 2400 watts and it worked just fine for mine

The other thing to consider is the weight.  If you need to move it around, The larger generators weigh more. Two smaller generators will weigh  a lot less and are easier to physically move.  The Honda 2000 weigh 40lbs.  The Yamaha EF2400 is 72lbs and the Honda 3000 is 135 lbs. You will have to decide what you are comfortable moving.  If you mount it in a fix position and rare ever move.  Then the weight is a mute point.

Also consider what other appliances you will want to run at the same time. If you have a generator that is just barely able to run the A/C,  You will have to turn the A/C off everytime you want to run the microwave or coffee maker.  So buy a generator that is sized to provide enought wattage for everything you will want to run at the same time.  This is why the Honda 3000 and the Onan 4000 are such popular units in LQs.