I have found 40-hole new-old-stock Dunlop-style 28" rims, in Auckland, NZ. no 32 hole rims though.

I have managed to find a good contact in Germany via German-language websites who is a guru on old bikes and may be able to help identify the Dreigang Torpedo hub (via the velo-classic site recommended by rhm in the post above - thanks). I just sent an email in English to what looked like the "send message" link on the website, and I struck it lucky.

I will probably get around the 32-spoke problem by having the 32 spoke old front hub laced up to a 40 rim, with care taken to miss out 8 spokes in a symmetrical manner. Any thoughts about this? I think it will be fine.

When I clean the rear hub I will take some decent photos and hopefully find some serial numbers/dates stamped on the hub casing