In Hyderabad,
Society for Awareness and Vision on Environment (SAVE) a NGO is working to make unpainted clay idols available at different parts of Hyderabad. Youth For Seva Volunteers will be helping out on this.  Refer to the link for more details on the work done Mr. VijayaRam of SAVE and involvement of  HMDA.
The 4 Locations [...]

Contact details of shops selling unpainted clay idols.

A list of shops making or selling unpainted clay idols of Ganapati,  or idols painted with colors obtained from natural dyes. This list has entries obtained by Youth For Seva volunteers, and other concerned NGOs, individuals. There is no sort of guarantee involved with respect to the nature of the paints used for the painted [...]

Shops selling Clay Ganapati idols in different areas in Bangalore