I think your best bet is just to call Winnebago or Lichtsinn RV. We don't know what model 2018 Sunstar you have so I can't tell exactly what you need from the parts catalog.
I did take a look at the parts catalog for a 2018 Sunstar 31 here:
https://catalog.winnebagoind.com/2017/300084.htm
You can flip the image over with your cursor and click on the part you need.
If this is the wrong model, you can choose yours here:
https://catalog.winnebagoind.com/menu/Parts.htm
You'll want to look at the "Exterior" page (click on the blue description)
Good luck.