I came to the racing forum as this is a piece I am looking to lower pressure on my Cummins. I have swapped the original a 98.5 Carter fuel assembly/pump that puts me close to blowing out the shaft seal on the Bosch VE injector pump. Is there such an animal? The pump puts out 18lbs if the gauge is right. Trimming it down to 15 is the goal. If you blow the front deal it floods the crankcase with fuel.

haven't been around here much.

I would think any deadhead style regulator that operates in that pressure range would work. I don't think it needs to be a diesel specific regulator since I know a bunch of people running normal gas pumps as lift pumps on their Cummins trucks...like a Holley blue pump for example.
Just a quick search on Summit's website showed only a couple of options in the 10-25 psi range and they were all around $200.
There's got to be something cheaper for this application though.

No doubt. I see "gasoline" on some things. I am guessing that's for the E85 folks. The Issipro boost and pyro gauges were crazy expensive.

Yes, I had an ISSPro fuel pressure gauge on my '01 Cummins that worked great, but was expensive. I put a cheap set of GlowShift gauges (boost, EGT, & trans. temp) w/ the pillar mount bezels on it that worked really well. Had them for about 7 years w/ no trouble at all.

Are you having trouble with the seals in the injector pump? If not why change the pressure? If it ain't broke, don't fix it
Have you tried asking about this on the truck forum on here? If not, I would