Well... First:
Are you sure there is no holding tank and never was one? (Where does it go) Having a toilet "on board" even if you have to be hooked to the park sewer (like a park model trailer) can be a very good thing when it's raining by the buckets and you really need to.. You know.
Second, There are now a few options on a refrigerator
Option one, A traditional "Absorption" unit (Standard RV- Fridge) I'm Sure you have priced those Run on propane or 120 volt (Some add 12 volt, not many) require around 350 watts when running on electric (NOTE that is not an exact number)
Option Two: Some new technology compressor jobs.. Run on 12 volt (some run on 120 with a built in converter) take aroudn 35-40 watts of power.. Work surprisingly well.. I have a chest freezer that uses this technology one caution though EXPENSIVE
Norcold makes these units,
Three, Traditional HOME TYPE fridge.. You can get small 120 volt compressor fridges designed for office or hotel/dorm room these work very well, need about 100 watts running, and around 500 watts starting, traditional compressor jobs.. Been some years since I purchased one but again I suspect you have looked at price tags
Motors like true sine wave inverters should you try to run it off battery when going down the road however... If you plug it in a day or two before you are ready to leave, get it good and cold, then put a packing strap around it before you climb into the truck, it's good for six to 10 hours (Depending on how new and the model) without power DOOR CLOSED
Do not forget to tie the door closed though
I had a small trailer so I took some nylon straps and rigged it so they formed a handle I could lift it in and out of the trailer with, Set it on a pad next to the trailer Worked great.. Very great. Last time I saw it the folks who are using it now were very happy with it, They pack it, cold, drive 200 miles, plug in.. Same as I did