How likely do you think it would be for someone to
machine the right
kind of blanks out of stock? Or possibly existing key blanks that
just need a few extra cuts on the sides?
It's really not going to be necessary to machine blanks. Download "Key
Blank Directory - Edition: 13" from here:
https://www.ilco.us/support/resources
and explore e.g. Yale keyways. The lock may not have been built by
Yale, but that approximate keyway shape is widely used.
De