I need to copy my existing one large( 24in x 24in x 18in) and bloody heavy terracotta pier cap. Does anyone know of a company that can make a mould of the one i have and copy it?
I think you might struggle a bit on that one. Stone pier caps aren't too bad, as there are still quarries that will carve a new one for you (at a price!)
Have you tried companies that produce hand-made roof tiles and fittings? Keymer for example make hand-made fittings, including items such as repro Victorian terracota roof finials. I'd prepare the wallet for a bashing though........
I've no idea whether they stray into your sort of territory, but it might be worth a phone call to Peter Minter at Bulmer Brick and Tile in Suffolk. They make bespoke bricks, tiles and shaped bricks. If they can't help, they might know someone who can.