till the company gets back to me Ive done this to mine.
Ive already a silicone cover on mine so i.......
1st get some clear flexible plastic cut out two squares and feed it into the back and the front of ye screen, of ye silicone tom,tom cover.

(its like fekin "blue peter" but without parental consent)
next get yer trusty silycunt gun and liberally apply to the inner sides of the cover to sandwich the inner plastic sheet to the tom,tom silicone cover.

make sure its gets to the sides of the cover to get a good seal.
cut out ye power fitting hole's smaller so there will be some water protection on the socket , ye mite have to put extra silicunt on these areas?
looks like this after..
(this is an experiment so i will accept no responsibility if any one uses this method n damages the sat nav tom ,tom)
am gonna try it on the bike later....i can always use a plastic bag over if it rains really heavy, but i recon its at least shower proof...
this is another UGG.TEK production, sort of
