Reuse a solar panel from calculator?
I used a multimeter and the panel shows 2 volts in bright light, the motor does spin with a 1.5v battery.

PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format.
You also have the ability to customize your PDF download.
You are ultimately limited by the power being received by the solar cell, which averages about 1400W per square meter from the sun, and indoors will be far less.
Try salvaging larger solar panels from old garden lights, these should at least give you enough power to charge a small battery pack.
That solar cell shows 2 volts at probably less than 5 milliamps...
2V * .005A = 0.01 watts.
almost any conceivable motor would draw orders of magnitude more power than 10 milliwatts.
https://solarbotics.com/download.php?file=58