Another one on my many to do list that finding reference photos proved to be challenging. I took as much as I could from the Battlefront game, toy models and any other pictures that were available on line. I cant say for sure that it is 100% accurate, but once again it is as close as I could get with the information at hand https://www.starwars.com/news/d23-expo-2019-jet-trooper-from-star-wars-the-rise-of-skywalker-revealed
As always do check the sizing suits your needs and although the STL came out a very stable model with some interesting textures it is for Thingyvere's reference picture only. The .3MF file is ultimately what you should use, but it is of course your choice.
Please note if you have paid for JACE1969's Jet Trooper and or found this model else where, other than Thingyverse. Then it has been stolen and is only available for your free personal use only and not for redistribution and or monetary gains.