To answer your question "yes."
I was in the same situation when we played where there was no PA and we had enough of an audience where I would have to shout - which happens occasionally.
Since the combo amp has only one 1/4" input, I used a very small mixer (Behringer Micro MX400; it's powered, but no other pre-amp), and a transformer (low z to hi z). I found a screw on mic holder that attached to my music stand, and I used a mic with an on-off switch.
The mixer needs to run both the bass and the mic, but then I could balance the volumes of bass and vocal. It would suck for someone trying to sing, but sufficed for announcements, introductions of the band and of course the subtle but persistent reminder that we did accept gratuities.
Hope that helps.