I played with Kwalus' design here. I wanted something to hold an off-center camera, like my ipod, and I wanted it to be a little beefier than the rubber bands. I used 1/4" x 2" nylon bolts to save weight and some springs I found at the hardware store.
The photos you see are of a prepared slide of muscle tissue. I used lenses from disposable Kodak cameras in my microscope.
I printed with PLA, using the medium settings. PLEASE NOTE: check the orientation of the parts before you print. I don't know why, but they are being displayed upside down.