Manhole covers price inquiry from Poland

Now we are interested to find a manufacturer of manhole covers and start cooperation.
We are particularly interested: to buy manhole covers of Gray iron and ductile iron Do you produce manhole covers? How much tons monthly could you produce?
1) We need manhole covers of Gray iron and Ductile iron. Inner diameter 600mm, height = 100 or 115mm, while maintaining class D400, ie enduring - 40 tons. weight as little as possible - is it possible to about 91 kg (gray iron)? Our competitors make such,