The windscreen on my Triumph Tiger 1200 motorbike came with rubber washers, one per fastening hole, that get lost easily.
When I take the screen off, a washer rolls away to disappear somewhere on the garage floor, well out of sight.
Quick and dirty replacements did the same.
If got sick of this, so printed some tight-fitting washers, for both front and back of the screen (ie two per bolt).
I used TPU. Work well.
ScreenWashers