In Hyderabad,
Emerald Mithai Shop at Indira Park and its branch at Kukatpally Housing Board are distributing small clay Ganesh idols for free as part of Eco-friendly Ganesh campaign. They will be able to guide regarding the purchase of 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