This is really strange a pond forum and nobody knows where to buy a pump.
I know where to buy a pump. I also know that there are short shaft engines, long shaft engines, splined shaft engines, tapered shaft engines, threaded shaft engines, keyed shaft engines, 3/4" shaft engines, 25mm shaft engines, and every once in awhile, 5/8 and 7/8" shaft engines. And those are just some of the choices common to 5-6 hp engines. In some cases, it can be cheaper and easier to simply purchase a new pump/engine combo.
Nevertheless, I would begin my search at Northern tool. May give you an idea of what's generally available.
