I ordered a black one from eBay. Under 30 dollars. Ordered some pex tubing and pex T's from amazon. I cut the hole in the same location as our last tt had the outside shower installed. I ran the tubing through the rear of the kitchen cabenets to T with the kitchen sink faucet. Works well.
Our last trailer came with a fold down rack on the back bumper. We use it as a counter top to wash dishes since it's outside shower was just to the left of the right tail light.
This tt came with an outside shower above the dump valves so out of the way for washing dishes and hands other than a dumping mishap. Here is a video I used as a reference. DIY Outdoor Shower Install
As far as the Pex. I got it from amazon but later learned lowes carries the tubing and fittings also. A live and learn would be not all pex fittings are equal. Prior to installing our kitchen sink water did not have a plastic taste in the water. After putting the two t's just below the kitchen counter now the water has a slight plastic taste. We use bottled water so not a biggie for us but they do sell the fittings that don't have the plastic taste they are just a bit higher. I also bought a cutting tool from amazon. Handy.