from 2013 till say about 2015 there used to be a strong foam sheet which was available with RC Bazaar which had lamination on both of sides and was huge in size. Lately they dont sell that anymore.   

Anyone has any idea where can i buy that sheet. is it available in Mumbai or Bangalore ?

Any specific Name for that sheet ?

VISIT RCDUNIYA.COM

And there ull see building material
And if i am not wrong kinetichobbies sell them as well
(Hobbypep as well)

Search search search... Thats what I could say...almost found anything and everything in my local market ... Please forgive me if I am wrong

I have some

have a look @ http://www.rcindia.org/for-sale/depron-foam-sheets-for-rc-plane-construction/