Hey Philip, I've heard Puig makes good windshields for our bikes. Mine is 2017 (Bonneville Bobber), and I was also researching this question for myself. Here is the one that should fit your 2018 (I was looking for the larger screens): https://www.motorcycleid.com/puig/up-and-down-windscreen-mpn-2193w.html
I will also attach a pic of that wind screen on the bike for you.
View attachment 203771
Thanks. Triumph actually does make one for the bike, part # A9700374. The dealer was unaware of it at first. I found an adjustable one from MadStad Engineering that I'm going to try. I'll post after I get in installed and tested.