Curtis Novak has started making a variety of Bi-Sonic/Darkstar replacement pickups:
 
http://curtisnovak.com/pickups/BS-DS.shtml
 
I haven't had a chance to try them and haven't heard of anyone yet that has, but I am very tempted to get a pair for my Guild M-85 II. They are pretty expensive though...

HI Harry,
 
Thanks for the information. Just last  week a pair of Dark Stars sold for slightly over $700.00 on ebay.