50 PSI (pounds per square inch) is a pretty hefty pump! 50 PSI is almost the pressure your household tap water is at. The maximum allowable static head pressure on a residential plumbing system is 85 PSI... At this pressure, you would require a minimum of 3/8 inch schedule 40 PVC piping Are you certain that is what you need?!?!

I suspect perhaps you meant a 50 GPM (gallons per minute) pump. These are very inexpensive, and can be purchased at any DIY store, pond shop, or well stocked pet shop for 30 USD or less. Multiple inlet outlet formats are available. Personally, I prefer the ones that have 1/2 NPT inlets and outlets, as these are easiest to rig tubing to with very nice looking "Prestolok" push to fit fittings.

Another advantage to these pumps is their small size and quiet operation. In addition, these can be plugged into a standard lamp timer for intermittent operation.