I believe BK have done something with magnetic poles (well, I know they did the pickup, and I think it had magnetic poles) called the Knuckleduster
But
It was an odd shape made for nathan sheperd guitars and wont fit any normal route.
The only pickup I know of thats readily available of the same basic design and is well regarded is the Swinseshead A.M.P. However, it seems swineshead are no more (shame, while BK are the best pickups going, swineshead were like the best kept secret of the UK pickup market - very good sounds).
Maybe, just maybe, you can get something rigged up for you custom.
Failing that you may be able to take heart in the offset winds that BK use as a matter of course to help impart clarity and attack to fat humbucking tones by leaving a few hundred turns in one coil uncancelled, single coil sound (while killing 60 cycle with the rest). All of them are asymmetrical to some degree, maybe the effect can be emulated with a highly asymmetric wind or can be found in BKs most asymmetric winds (like the VHII for example, I believe thats quite heavily offset).