look in to Netafim for low psi valves here is the link for the valve

http://www.netafim-usa-landscape.com/Landscape/p-valves/p-valves-aquanet.php

Here is a link that might be useful: go

9MileCrk,

My $0.02 worth is to stay away from drip and go to furrow/flood irrigation. As long as you are not concerned with irrigation efficiency as your bottom line. Run hoses with no emitters to the furrows between your plantings and let the water run down the furrow. You need to have a slope of the furrow at about 1 ft of fall for every 100 ft of run the water will make it. Your soil can't be too porous though. Or build up the sides of you furrows to have enough head on the water flow to move it to the end. If your soil is porous. Line the furrows with PVC pipe cut in half and cut openings at the plant locations. Easy to experiment with this method first before going the expensive drip route.
Hope this helps. Aloha.