inexpensive dissecting microscope?

Hi,

Does anyone know of an inexpensive dissecting microscope that is
suitable for very basic C. elegans work? My wife has used C. elegans
for several high school lab projects and now has a small budget and
wants to purchase 10-15 scopes. They must be suitable for picking
and easily distinguishing, for example, males from hermaphrodites and
unc-22 mutants from unc-30 mutants.

Thanks for you help,

Brendan
Horvitz Lab