Where can one find vermiculite?

[Karakorum]

Is there anyone who knows where to buy vermiculite in blocks or sheets? I plan to use it in a fireplace.

 

[thoeke]

Today I bought at Luddwes Hushållscenter 0455-308990 (appliances store connected to one of the larger chains for appliances)
outside Karlskrona one board 100x33x2.5 cm, surely available in other sizes, they can
provide info about the Swedish wholesaler, the boards are made in Denmark, the board cost 500 money.