A Suggestion:
Just wire a heavy duty extension cord into the A/C switch (that's assuming your RV has a big switch to switch between the front and rear A/C). Or you could just run a separate wire directly into the rear A/C and have it available to plug in the extension cord when needed. A simple relay lock out (like an ATS only smaller) is recommended so both wiring setups can be used...the original OEM version, and your additional wiring. (Contact me for a drawing if you want one).
Then when you're at a RV park, plug the new extension cord into a 20 amp outlet. Either at your power station, or the next RV spot over.
Of course you clear this with the RV park management if necessary. Some parks will ask you to pay for a 50 amp spot but that's really not fair since a 50 amp spot supplies 100 amp, not just 50 amp. Whatever, you work it out with them for what's best for both of you. I see it a lot these days. A 30 amp RV cord and a 20 amp contractors cord from the power tower to the same RV. There's really no safety issue for anyone or anything. If it's popping breakers, that just means you should plug into the neighboring power tower. Usually...YMMV.
Much less expensive or labor intensive to do it that way.