When my ETA died, I documented it
here. Over the years, other MB owners have written to me and I've posted their results.
IMO, the best is
Beckmann Industries but, unfortunately, they're the most expensive.
You might try S-Class Eddies
here. He consistently has good, used and reasonably priced S-class parts.
Victor has helped a lot in this forum and his prices are reasonable for a re-wire of your ETA. Check it out
here.