Frank de Rek in the Netherlands is offering NOS 6V replacement horns for sale - see
https://www.generaaltjes.nl/Adverten...claxons-6-volt and the pictures below.
These were manufactured post-war as a replacement part for part number G503-77-43681 and they look like an acceptable replacement for OEM Ford CMP horns. And at EUR 40.- they are affordable.
If you want to order one,
please email Frank and let him know you've seen them on MLU Forum.