I've been reading up on electric ducted fans as used on a lot of the latest RC model airplanes and some of these things are putting out 3.5kg of thrust at 100a using tiny lithium ion batteries. I have no idea how this would translate into boost on an engine but the idea is intriguing. They usually use an extremely powerful brushless motor with a gearless axia fan spinning at close to 50k rpm instead the more traditional roots (supercharger) or centrifugal (turbo) fan.
EDF Schubeler DS-94-DIA HDT Fan - DS-94-DIA