Talk boxes were often custom made for famous performers by connecting a plastic hose to a compression driver like this one. All you need is a few PVC fittings, some plastic tubing and an amplifier to drive it.
Show Me the Way
https://www.google.com/search?q=DIY+talk+box&oq=DIY+talk+box&gs_lcrp=EgZjaHJvbWUyBggAEEUYOdIBCDQxMTVqMGo0qAIAsAIB&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:83df68db,vid:1PcL2ZdqU5k,st:0