Any hints for a suitable solar panel and how that would work?
I wouldn't have thought that a solar panel would work, I don't know how you'd interface with it, a small dot on it wouldn't produce much current...
You can get larger LDRs:
http://www.rapidonline.com/Electronic-Components/Optoelectronics/Photodetectors/Light-dependent-resistor-NORPS12/34793/kw/LDR
About 10mm sensing dia. I am using them for my project...
Mowcius