I have two small ponds at our front entry. I bought my pumps from HD (any box store should have them)...I think they were standard "little giant" or eqiv. The good news with buying them there is I have burned out two pumps and both have been replaced without complaint. Maybe that is because of what I spend there [img]/forums/images/icons/blush.gif[/img]. At about $60 a pop, it is worth the convenience of easy returns if you have problems.
By the way, I solved the clogging problem easily enough by putting the pump in the middle of volcanic rock in one of those big black nursery planting pots scooted under the waterfall....acts as a macro filter that I clean out once a year. Also planted the upper pond heavily, which acts as further filter. In our third year now with no worries.