What problem are you trying to solve? If it's a perceived pressure issue, make sure you're using your RV's pump and fresh water tank... not an unknown campground water connection.
You can get very efficient shower results with a properly designed shower head. Flow rate alone won't necessarily give you a quality shower... like standing under a 5/8" garden hose with 100psi. Lots of WATER... but it isn't going where you want, AND wastes a lot of water in the process. Spray pattern is an important part. Some "low flow" shower heads have an excellent spray pattern. You just have to find the style you like.
We've used the Oxygenic shower head for several years with good results. But there's a bunch of similar options.