a garden sprayer?
some have an interchangeable nozzle (and thus you can make a pretty nice jet)
and even with a safety valve you can get a pretty sharp stream of water...
20ft should very well be doable, aim is on you though
I'd say because they're cheap and readily available in nearly every other store...
just see what you can find and give it a shot (hehe)
'sid
PS original super soakers are still on ebay ... sooooo if that's more to your liking, go for it