The stator "passed all tests", but you didn't check charging voltage at the battery? >12.5 at rest, > 9.6V cranking, 13.5-14.7 running at 2K RPM or more.
If it's charging while running and you are SURE the cables are tight and clean, the VR can have an intermittent fault as well, just to frustrate you more.
There are early and late VR's with different plugs for whatever year your bike is.
I put "Buell voltage regulator" into e-bay and got this for a bolt-on solution:
https://www.ebay.com/p/9037306963?ii...iABEgJ7CvD_BwE
You don't need a CNC machine to make a simple bracket, but a VR is a pretty universal part. They take the A/C voltage you tested for on all 3 legs on your stator, converts to DC current and "regulates" it to 14.7 max. Theres 'upgrades' available, but its a pretty hardy Buell part and a new OE unit should last you.