YES I got the required files and NO, I am not burning you copies.
You can contact Francois Davroux on the site stated above. After you pay him his software fee, I am more than willing to burn you a copy in a 28C64 PROM. These files are traceable due to their personally assigned serial number. I am willing to build/modify your board but only after paying the Davroux brothers.
Reversing the modified speech board is easy; just stack your 2 Gottlieb files in another 28C64 PROM and just swap them out. That easy? Yes, that easy.