I used a solar cell from another vibrating solar powered bug which can easily be found on the internet and used it on a Hexbug Nano.
It moves around as quick as when it was battery powered!
Step 1: Adding the Solar Cell
Just solder the wires red to positive metal tab & black negative to the other metal tab, use the battery as a polarity guide.
Screw the battery cap back onto the bug.
Use double sided sticky foam to secure the solar cell to the body. Balance correctly so that the bug doesn't topple over.
If anyone can tell me how I upload a video I will post this little guy moving around!