Pressure Washer Demo Unit

Hi, I wanted to make a demo unit for stores, so we can demo pressure washers in store for people to use and try. I did not want to use a hose pipe, but i wanted it to be a self contained pump which pumps the water around back into the pressure washer unit.

I wanted it know if thats possible regarding the PSI of the pressure washer.

Also how much will a pump cost?

If you can get back to me that would be great.

Thanks