I have this
. I bought it for a Casio E100 a few years back. It works exactly as advertised with a Casio.
I tested it with an Ipaq also but it didn't charge.
I could test it with the Zaurus and let you know.
Yes, the CF101-A charges a C3100. The orange light stays solid when the Z is turned off and pulses(flashes) when the Z is on, and pluged into the solar charger.