Well the sample chips arrived today and I set up the prototype board on the bench with a small hand mic input and a switch to bypass the board. I'm pretty happy with the sound and the two adjustments allow a very wide range of effects that (to me anyway) sound very much like the original.
I'll send off the protype for installation in a machine and see what the owner of the machine thinks? If that pans out OK I will have a batch of boards made.
Here is a video of me first speaking a few phrases used in the machine and then the same phrases with the sound effect enabled:
