[Eric T]

While poking around the interwebz, I came across this article: http://speakyssb.blogspot.pt/2011/12/pow...-leds.html where a guy uses a standard LED to produce voltage like a solar cell. 

I tried it myself, and I get 1.4 volts max out of a white LED with a light up close. 

Next, I connected it to my o-scope and quickly waved a flashlight across it. I got decent deflection with the light. I'm going to need to do some more experimentation, but this seems like it might be a promising way to replace the photocell. 

Edit: Or maybe just try out some photodiodes or phototransisters. Derp.

I still need to do something about the rubber for the drive bell.