I have been trying to find a solution to this problem as well so would be interested to hear any recommendations.

I regularly play both acoustically as part of a duo, and with a larger band with electric bass and percussion. Amplification is definitely needed in the second situation. I have been at quite a few venues now that demand you to plug in just to play solo with an acoustic guitar or banjo (which I think is mad, and probably just done because there is little expectation that an audience will remain respectfully silent and listen but that's a separate issue).

I agree that a decent mic is a good option, but it's restrictive and not always available.

Is there anything that:
1)Can either remain on the Banjo at all times without affecting its acoustic sound, or be easily and quickly removed and
2)Can plug straight into a PA and give a decent sound?

If it's possible to do this for acoustic guitars, why is so hard to find a solution on the Banjo?

(Please no more predictable Banjo jokes!) ;)