I'm fortunate to have 2 lab-grade orbital shakers. They're decommissioned, but good enough for my use. 
Each can fit 4 2-liter flasks or 4 1/2-gallon pickle jars. Or 2 1-gallon jugs. Pretty much any vessel will work. No stir bar needed.

Each can fit 4 2-liter flasks or 4 1/2-gallon pickle jars. Or 2 1-gallon jugs. Pretty much any vessel will work. No stir bar needed.