What I needed was a stand which would do three things:
1. Hold the microscope so that it is perpendicular to the table.
2. Hold the microscope rigidly.
3. Provide a focusing knob, so that the focus can be adjusted accurately without disturbing the specimen.
I wanted a small rack-and-pinion mechanism for the focusing. I considered several options, including re-purposing parts from an old photo enlarger. In the end, it was the same vendors on eBay from whom I bought the microscope that provided the missing parts. I got a macro focusing rail that was very inexpensive and fit the bill perfectly.
With the microscope attached to the focusing rail, all I needed was a rigid stand to hold it in position. I built a stand out of laser-cut acrylic. (I made it at TechShop. www.techshop.ws) The result is a handy microscope that's easy to use and cost well under fifty bucks.