I've recently been through this very question.... There are a few alternatives (obviously). On the cheap end of the scale, I've been told that a Sicce IDRA pond pump works - there are threads around on this one. pictures even I believe. I've been quoted about $70 to buy and ship one from Adelaide to perth from this guy firstname.lastname@example.org. OR, you could get a 'real' one. I just ordered a March polysulfone pump from morebeer.com which is $155US + postage - search for H375 in their web site.