Maybe I figured out something unknown, maybe this is old news...
I spent Sunday looking at turn signal lenses on the fronts of ~1965 Triumph Spitfire and Austin Healey cars, wondering if they are the same as the pre-September 1969 Bellett GT.
I found an auction listing, the description says it fits a long list of British cars, and it is made by Lucas. That brought back a little detail from the Asaoka interview article, in which he says the electrical and switch gear was all from or inspired by Lucas.http://www.ebay.com/itm/200831984281
It's worth a very close look. I will have to measure one, and maybe contact the seller with some dimensions. I have to make new bases anyway. Even if they are not exact replacements, they might make a good substitute.