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)...
Hi everyone, I have recently picked up a 2017 Triumph Bonneville Bobber with only 1200 miles on it. Now, while the bike is new to me, I registered on your forum to learn from you folks and get ideas on mods and add-ons.
Cheers!