I used the Watt's pump at the 1st link below. The motor can be timed, switched off, or run continuously.
Iirc, I shopped and found it for $125 ish on ebay. Beware, some vendors list it as plastic. *Afaik*, the casting and impeller on the #500-800 are brass. Double check though. The instructions with the blue paint over brass version that I have specs 120* water max, but it's fine so far at far above that. There's a thread here somewhere with pics of my install, but I can't find it.http://www.lowes.com/webapp/wcs/stores/ ... ing%20Pump
Here's another candidate that I know nothing about.
This link is broken, either the page no longer exists or there is some other issue like a typo.