I believe I have found a replacement fuel pressure regulator for the 6.0 V12 fuel rail. It is exactly the same size as the original, regulates 3.17 to 3.3 bars of pressure (just a little high), and is readily available new. However, it does not have the vacuum pipe attached and you will have to fabricate that. I have purchased one but have not fitted it yet as my original is still working. It is a part for a John Deere motor. It is available on Amazon for just under $20.00. Copy and paste to find it.

Fuel Pressure Regulator Compatible with John Deere Gator 590i 625i 825i 850i 860I 2011 2012 2013 2014 2015 2016 2017 AM136612