Sorry to hear you are stuck in the situation banjo players sometimes get put in. I don't think there is any "good" sounding acoustic pickup. The Jones and similar types seem to come the closest, but I've not yet heard a banjo sound like a "good" banjo through one, regardless of how good the player and the banjo actually are.

The solutions people have tried produce mixed results, always trading off "real banjo sound" for volume. One possibility is to play to the *audience* with a microphone, and have the people on stage, yourself included, hear you through your pickup. That means at least the audience will hear your better sound, even if the people on stage don't. Less than satisfying, but a solution of sorts.

Then there is the solution of ear monitors, used by all on stage, where mics don't need to create feedback because all the monitoring is done by headphones the performers wear (this is getting increasingly common, even in bluegrass). Quite a project to do, and not everyone finds this the best solution, as wearing earphones on stage has definite disadvantages. I doubt your band would be much interested in this.

Pete