You can use "bladed" humbuckers for citterns, bouzoukis and mandolins. try the Seymour Duncan Hot Rails. Or Dimarzio - try the Cruiser strat-sized humbucker or the X2N high-power humbucker (if you must...).
Alternatively, I highly recommend Catswhisker pickups for custom pickups. The man hand winds them himself with an electric motor and a steady hand. Get him to make you a special pickup.
Thirdly, I'm selling a 60's Fender Mandocaster. Like a miniature pre-CBS strat in mandolin form. Its not cheap though... Its going to Vintage and Rare guitars in Bath soon, but I'd rather sell it privately to be honest.