Try ebay..."wiper arm cover"
I found many pages of 50 each, wiper parts.
Your photo looks like a Porsche 911--928 cover. You could use duct tape :)
But that will give you a place to start.
The valves are under the entertainment center. Open door, remove side-wall and you are at the back of the water heater. Upper and lower check valves.
Been there done that. (We are on the road so can't send photos)