Best campervan foam

[wolfbus.uk]

I put an order for some foam in with an Ebay foam company but alas the order has been misplaced. I can't be bothered to use the same company as I get sick & tired of shabby sales service that seems to be the norm these days.

Anyone can recommend a company or type of foam for a Devon bed. I need 3 inches of foam for the seat part & 4 inches over the engine preferably medium firm as I sleep on my side & have a disabled shoulder.