We camp mostly at electric-only sites which means taking on water at the campground. The Camco hose adapter that you are supposed to ram down the throat of the Camco 37002 gravity fill at the back of the Scamp
always frustrated me. It wouldn't stay put unless held and often kinked due to the weight
of the hose.
My solution was to sweat together a 90-degree elbow to a short length of tubing then a 45-degree elbow and another short length of tubing. I cut off all but about 1.5" of the clear fill tubing and joined the clear tubing to the 90-degree elbow with a hose clamp.
The finished product rests on the rim of the fill bowl and does not jump out. The small section of clear plastic allows the sight of water flow.
I imagine the same could be accomplished with PVC. Apologies if this has already been posted somewhere, a very quick search did not return anything similar.