I stumbled upon this today.

Depron: http://www.kwalityproducts.in/16_Depron-Foam-Sheet.html
HD EPS: http://www.kwalityproducts.in/10_12.5-mm-EPS-Thermocole-High-Density.html

Firstly, has anyone bought from them before?

Is the depron fairly priced? Is there a cheaper option available anywhere else?

They don't have HD EPS thinner than 12.5 mm or I might have tried some. Is  12kg/m3  stiff enough?

After seeing their website about 4years ago, I visited their shop but found that they did not stock the product. Why they continue to show it on their website is strange. Try your luck. They might have some in stock now. Just be careful.

Cost is extremely  on the higher side.

I too visited their shop a couple of months back looking for depron and HD thermocole, they quoted 4-5folds higher than what I had bought earlier and when I said that, they quoted lesser and said it is only available in large quantities. Spooky! finger on my nose!

Edit: they are not a small shop either, and deal with almost all types of foamy stuff!

Thanks everyone!

So, which is the cheapest source of depron/ biofoam in India if I wanted to buy a considerable quantity of sheets?