Im trying to find some cheap cheap water projection screen for laser
or video  show...there is a certain kind of nozzle and strong pump
that mists a screeen

You might want to get a quote from Tsunami Water Screens:

http://www.tsunamiscreen.com/

simple 

go to your local gardening center and get them to hook you up with a
chain of plant misters you can suspend on a wire. you will also need a
high pressure pump. should cost less than $200 i suspect. Remember due
to image trasmission through the thickness of mis best viewing will be
within a 30 degree angle as measured from the plane of mist screen


happy viewing! you have insired me to build one in my garden this summer!