We use polar screens and work very well and they are a very good price, there is a youtube factory tour by someone , they do not list Transit custom , but they do sell make them to order
We've used the front and year window screens from rainbow screens. Although pricey they're been Amazon and it's one of the best purchases we've made for the nugget. Keeps us cool in the heat and warmer on color nights. Zero issues with condensation too when we use them