If you have the old doors, you could use them as a pattern. If not, measure the area and decide your style. You can go with something like these panel doors:
Perhaps you can get some inspiration from this post. https://www.mtnmodernairstream.com/single-post/2016/08/24/Cabinet-Build-Out
Is this what you had in mind?
You might be able to pick up some old ones at a Habitat restore that you can install and would save you trying to build some. You could also paint existing ones if you just want them to have a new look (if they are not missing or damaged).
If you could find old airstream trailers maybe you could buy the cabinet door fronts cheaply
here is another idea
If you have a recycling collection area in your town, you can check them out for cabinets. It is free to go there. I think it would be easier to get some old cabinets and then secure the doors with magnetic closures than to build your own cabinets.
It is important that replacement airstream cabinet doors are both lightweight, and stay firmly closed when the trailer is on the road.
It is unlikely that recycling collection depots would have doors other than for standard residential kitchen cabinets.
What is wrong with the present doors that they need replacing?
They were the plastic type that rolled up and down and were in very poor shape.
Take the original doors off and measure those with the new wood then sand them and paint then take the old hinges off and put on the new doors