A water pump is a water pump. There are difrent models that have various flow rates, make more or less noise and have diffrent Amp draws.
The best rule of thumb is least expensive is lower flow, noiser, higher 12 draw. Quieter is more expensive, with better flow rate and lower power draw. Any RV place will have on that will work, but you need to have an idea on what you want/need. Best place for basic research on the web is good old
www.campingworld.com At least you can see most of them there. If you want a good price with free freight to your door try
RV add ons The link should take you right to the water pump pages.
The pump is usally screwed to the floor/wall/ a shelf and has 2 flex lines and hose clamps to the input and output of the pump. Then there are the 2 power wires. Your pump is likely under your kitchen sink attached to the exterior wall of the trailer on a shelf.