fuel part/ locate?

Where can i find a schrader valve core for the fuel rail -goesn inside -on many dodge caravans voyagers etc? Is same on many many cars for fuel test..
No dealers sell it and the ones in the stores for tires and air will NOT work if you want to be able to do a pressure test--stem top is shorter-

-any info is appreciated since my old one was leaking and i need to get a new one ASAP!
Thanks

well i went and got the correct -so i thought-fuel valve core in schrader valve from junk yard and replaced the fuel pump AGAIN-2nd -ran 100 miles then replaced schrader valve so i could get a readind on psi ...and it showed low psi then in a test run---total failure and no start on side of road!!! ..towed back
What do i need to look at next .? the pressure on 2nd new pump was still 33 psi at port and after tank(oddly it went 100 miles on 33 psi) but when i changed that valve it went 1-2 miles fine then dead ..no fuel...Pressure regulater is functioning normal at 5-10 psi more when disconnected and no leak..
Any info on what to do next im so fed up with this issue? !
Thanks !