Where can I find a very small, adjustable boost switch to adjust from 4 to 8 lbs

[yellow95]

I want to be able to very my ON point with my water injection from inside ala SMC. Where can I find a small vacum/boost switch that is adjustable.

 

[galoush]

boost switch

I have a boost switch that i got from ATR , its made by Vdo and sdjusts from the top with an allen key for desired boost , Try ATR there # is on the turbo buick web page in the vendors list.