The best one from my experience (turbo ford, GN, and now my dsm) is on weyouput together yourself. Run a solenoid valve and fuel injection hose.
There are probably cheaper deals out there. Heres what a quick googal has provided:
(adjustable peak flow pressure via allen screw)
(controls activation via boost: Its adjustable!!!!!!!)
McMaster and Carr nozzles, Catalog page 1898 - 1901
#'s GPH@40psi GPH@100psi
3178K81 0.63 1.0
3178K82 1.26 2.0
3178K83 1.90 3.0
3178K84 2.53 4.0
3178K85 3.16 5.0
3178K86 6.32 10.0
3178K87 9.49 15.0
(nickle plated nozzles are best)
A few screwclamps and possibly a tank if you don't tap your existing windshield wiper reservoir
The key is activation point and choosing the proper nozzle flow. Activate the hobbs switch at a boost level that will allow the pump to flow enough injection yet will not bog the engine. This takes time to get down.
This homebrew system has gone thru 3 cars and 10-35 psi of boost for 6 years. Water injection, water/alky mix, pure meth injection.
$160 total including shipping. Add the cost of hose, clamps and fittings. You're still probably under $180. And the setup works for years. . .
For the longest time I didn't even run a solenoid valve, I just ran a check valve. It did good. But got clogged over time running meth (ate away at the rubber hose). A good fuel filter (that can handle the psi) just before the check valve really helped this. So you can subtract the cost of a $35 solenoid. the check valve I got was around 10 bones.
It allowd me to run 22 psi w/ stock 450s on a small 16G and stock intercooker(not a typo), stock fuel pump stock everything!!!) and I ran good and lean w/ lots of power on a hacked maf. . .