I would think, as you probably have ruined the sound anyway :-), that you'd might try a cheap Zoom multieffects pedal.

No way to tell what sounds good on an electric banjo, so the multieffect stuff gives you good options to dial in something that might work.

Your story doesn't say how you are recording.. but if you are recording on a computer, get a multieffects suite like Line6, Guitar Rig, Amplitude or something similar. That way you won't have to invest in something just to play electrified banjo, but can use it for different stuff..

You can actually download Waves Solo for free, to try out just for the recording: http://www.wavesgtr.com/html/product_gtr_solo.html

It should be of sufficient quality for this particular project.