Come to think of it , the Ford one can definitely be made to work as they sell all the surrounding items such as the window channel and the winder handles that also look identical to the original Bristol items
Anyone going on holiday to the USA that wants to bring home a suitcase full of regulators ? :-)).
Alternatively this UK company may be able to help
Ford Model A | Window Winder parts Parts | Model A Ford Parts Spares
The 406 onward regulators are a different story and they more closely resemble Jaguar / MG regulators of the era --- I used the bits from an MGB to fix my 408 window