OTB: Sorry for the delay. Took ages yo find that parts catalog.
Catalog Number 10-107
Mercedes-Benz Type M108
Edition A

Table 5, Groupe 7, Page 28 only shows the whole carburetor no exploded views of parts.
However Page 28 just "Fuel by-pass valve" as part 00-070-11-46.

I would suggest that you contact the Refactory and see if they can help you. If not, contact the folks at Mercedes-Benz Classic in Southern California 1-866-622-5277 or email them at classicparts@mbusa.com.

The reason to not diy this job is that failure probably results in fuel dripping from the carb to hot headers. Pennywise and pound foolish.

Good luck