I have not done this myself, but a year or so ago I was looking to get a CIEM and had spoken to the company about this (64 Audio in this case, I am sure same applies to others). I also spoke to several audiologists and hearing centres here as I also wanted to save on shipping costs. Most audiologists have, or have access to, 3D scanners which are used to create 3D files of physical impressions - which is often used for the making of hearing aids. They said it was an easy and quick process to take the mold and get a 3D scan of it, which could then be sent to the IEM company.
So I'd check with local audiologists or similar, and also with the IEM company if they can accept a 3D scan of a mold.