Open Mic / pub jam in Toronto?

I just found out that I have some business travel that is going to strand me in Toronto (Mississauga, actually) on the weekend of December 2nd.

Does anyone know of a pub that holds an open mic or jam session type event on that weekend.

I'll be travelling light, so won't have any instrument with me to join in (to the extreme relief of the paying customers I'm sure), but I'd like to attend and take in the music.

I will have a car, and I don't mind travelling a bit from the airport area.

Or does anyone have a gig that I might drop in at?

Also, any impressive music stores in the area that I should check out?