Spending more than $100 sort-of defeats the purpose of collecting rain water to begin with, so something like a convertable jet-pump (minimum $250 around here) is out of the question.
There are some 1/6 to 1/3 hp sump pumps that I can get for $50 to $75, but I'd have to modify them so I can attach an inlet hose (most of my drums are sealed with only a 2" opening at the top so the sump-pump can't be dropped down into the drum).
So - can a sump pump be modified to be able to draw water from an inlet line - or will priming it be a bitch? And can then generate enough pressure (what - 20 to 40 psi?) to drive water through a 50-foot garden hose and a single sprinker head?