Go to
The Water Filter Store and get an adjustable, a Valtera, or, better yet, a Watts. The Watts can be rebuilt if it ever fails. Set the pressure to 45 psi to 55 psi. The RV manufacturers usually recommend 45 psi, but the pumps nowadays come set to 55 psi. I called Winnebago and asked about 55 psi and they said that was fine.
The Watts X65BG is the new model of the regulator I have. I recommend it. I am happy with brass. I would not pay extra for stainless steel. Brass has been used with potable water systems for generations.