Keeping fridge cool in high 90s temps

Typically, this means a Norcold is installed wrong.

There are very specific installation instructions on how big the vents need to be as well as how big and what geometry the "chimney" is.

Unfortunately, if you don't follow those to a T, the Norcold can under perform.

I've had all my Norcolds over the years in well over 100F temps keeping ice cream frozen and foods cold.

You may have to fix the bad install to get the proper performance.

I got a rectangular "shade sail" at Harbor Freight and rigged one edge to attach to the top edge of the slide and pull the opposite edge out at an angle to attach to tent pegs. The shade on the side of the trailer helps the fridge a lot.

I also try whenever possible to set up so the kitchen side is facing East or North; away from the afternoon sun.

Is your frig in a slide? If so you will probably have two access doors so you can remove the lower one when parked to get a little more air flow. Next if in a slide do you have a slide topper? If not get a small tarp and cover the top of the slide and slope it down to shade the side of the RV. Best your going to get short of getting a box fan and putting it so it blows into the bottom access area.

My methods are positioning the TT to avoid afternoon sun, battery operated fan inside the fridge, making sure the chimney is clear and adding a fan to pull air out the chimney.