Yesterday I added a sprayer for the toilet bowl for those times when a regular flush doesn't completely clean it. We had one in a Winnebago Aspect some years ago and it was a great and handy feature.
(Wish we still had that Winnebago, given all the problems we've had with this Thor Axis.)
So, I bought a standard kitchen sink sprayer with a 3' hose, a 3/8" 'T' fitting and 3 small stainless hose clamps. Located the water lines in bottom of the bathroom sink cabinet. Cut the cold water line and installed the 'T' fitting. (Be sure water pump is off and no outside water is connected to the RV before cutting the cold water line.) Drilled a 5/8" hole in toilet side of the sink cabinet for the sprayer hose and attached it to the 'T' fitting. From a scrap of wood, I made a block for the sprayer holder and attached it to a shelf behind the toilet.
Materials cost about $22. and took about 3 hours time, including a few breaks because I'm OLD.
See pic's for details.