This is basically what you need... it is pretty much the same thing that Kent (M***s*rce) sells. If you have more than 50 psi difference, you will need shims to compensate. I have no idea where you would buy the shims. Perhaps Greezer can comment.

https://www.ebay.com/itm/Diesel-Injector-Nozzle-Pop-Pressure-Tester-High-quality-0-400-Bar-Pr-Gauge-/222060394684?hash=item33b3d4b8bc:m:m4J1buu_fHychDrQUcxGP2A

https://www.ebay.com/itm/Diesel-Injector-Nozzle-Pop-Pressure-Tester-Genuine-AG-Precision-Eco-Model-New-/222353849789?hash=item33c5527dbd:g:96oAAOSwb0hZ3dUM

https://www.ebay.com/itm/Diesel-Injector-Nozzle-Pop-Pressure-Tester-Dual-gauge-Bar-PSI-/122433196785?epid=730275844&hash=item1c819652f1:g:WDMAAOSw2N1Zwdwg

Dkr.