To piggy back off what nervoustrig is saying, they supposedly sell high pressure kits that bump the output to 1000 psi + you can add about 150 psi of shims, according to their manual. However, I was unable to find their high pressure kits in stock anywhere.
For anything higher pressure, it appears that McMaster part number 9712K112 is the closest fit for a Belleville washer option, though they're wayyy more expensive than the Ninja size Bellevilles.
If there's a way to use Bellevilles, that would be cool, cause the Hero2 regulator is extremely short. Like, a good part of an inch shorter than a Ninja reg, and well over an inch shorter than the cheapy reg that came on my 13ci Pepperball tank. Going from an aluminum tank to a carbon tank that's moved almost an inch closer to the center of the rifle can completely transform the balance of a bottle gun.