Peter, wax lettering for concrete casting ! there used to be a firm somewhere in Cheshire that made wax letters / numbers for concrete and plaster casting you just stick them to your base mould and cast after casting the letters are scraped washed out with hot water. that might be a cheaper way to do custom castings.

A small cnc desktop machine would be ok to make masters moulds in silicone so you could cast your own letters / numbers. Been more than 20 years since I sold my precast concrete business and totally forgot about the wax letters until I read Robs post.
Mike