Battery charger circuit page 01 :
Ni-Cad Charger for Solar Cell Radio by BD140

A solar cell radio used a 3V (or two 1.2V) Ni-Cad battery in it. The battery can not be removed. It use a mini jack socket for charging. Its quiet difficult to find such a voltage charger. Here is the circuit to convert the voltage from the general power supply.

Source : http://www.geocities.com/dsaproject/electronics/cook-book/cook-book.html