Actual incubators for microscopes cost a hefty-sum and so I have taken it upon myself to build my own incubator for an Olympus Fluoview inverted confocal microscope.
My first step is to build a cardboard enclosure for the stage and lenses (I am currently at this step). The second step will be to add doors and refine the box (maybe use a better material). The third step is to hook up a thermal controller ($30) and a hair-dryer to the box and test out how evenly the inside warms up.
I ran into some difficulties with the left side (user error), so depicted below is the right half of the incubator box.