Is there some alternate bracket that can be purchased that would allow it to be mounted via the existing holes in the frame where the water bottle bracket would go?
First, Kryptonite makes more than one U-Lock (at least 6 models) and more than one mounting. So, my first impulse would be to check the Kryptonite site or inquire at a local bike shop that carries the Kryptonite product line.
Second, Does the lock really need to mount on the frame? If the bike has a rear rack, the lock could get bungeed there. Or perhaps in a pannier? Or backpack/messenger bag? Jersey pocket? And, just sayin, the hipsters around here keep U-locks in their back pockets and that's for fun. ;~)
Not to be rude, but U-locks can be mounted or carried in a few places. Personally, I don't carry the U-lock on the water bottle mounts...mainly since I actually do want water bottles to be on the frame mounts. But hey, it's up to you.