Re: anyone have a dodger or spray cover on their inflatable?
I have never seen one but I bet you could rig one. It is hard to tell by your pictures but do you have metal rails on the side?
If so, you can probably find some bimini top hardware to rig a mount to the rails. The dodger tops mount just like a bimini top but then they snap down on the front and sometimes on the sides.
If you inflatable has a wood floor you could mount snaps to the floor. If not, you might be able to rig up some type of velcro mount to the floor. The velcro may also work for sealing the sides to the boat.
A canvas shop might be able to design one for you or if you are handy you could look for a used one and modify it yourself.