Need help with replacement

Working for an elderly lady who moved into house with a small (4' x 6' 2-2 1/2 feet deep with small waterfalls at each end. The pumps are labeled PumpMate 260 US and PetMate.com. I have searched the internet and cannot find any info on these pumps, and the site has only pet items. One of the pumps is putting out water but with no pressure behind the flow. the rise to the waterfalls is less then 4-5 feet and the pump stopped getting the water that high. question. do you feel these pumps are rated at 260 gph. and what pump do you recommend to replace one. these pumps have threaded output for what looks like either 1 1/2 or 2 inch connection. thank you . lost in the pond.