Hi dave,
This is so annoying, I've investigated this extensively.
In a nutshell I'm sorry to say its nearly impossible.
If the bore size doesn't get you the bolt pattern will.
I've had vehicle components, alko and a few others all try and hunt this down with no luck.
The overall offset was the one thing that wasn't the issue.
I've been trying to do this on 10" brakes, apparently there is someone that does it on disc hydraulic brakes, but never found them.
If you find something let me know, but I don't think you will.
Cheers
Justin