Hi,
There are some larger PV suppliers with wharehouses in Phoenix. You might check the local Craigslist.com and see if anything is listed for solar panels. Most are for installations in homes, but some might be RV installers.
You might check
RvSolarElectric.com in Scottsdale. I bought my first solar system from them many years ago.
SunElec.com also has a huge wharehouse in Phoenix. You might be able to pick up some panels there, and either install them yourself, or consider having it done in Quartzsite. They have great prices on solar panels.
Your RV will use about what 1 120 watt panel will make in a day - to run the refrigerator, CO and propane detectors. A couple more 100 - 120 watt panels will run the TV and can be enough to run a microwave.
However I never recommend running the microwave from a inverter unless you have a much more expensive pure sine wave inverter. My microwave was damaged by my modified sine wave inverter, and I had to replace it. Now I only run the microwave from shore power or generator.
400 watts of solar is normally plenty of power. I rarely needed to run my generator or charger while full timing - except a small amount of time in January. If I had been driving that week then the engine would have made up the power, but I was parked all month.
Fred.