Long shot, but try the M-B Classic Center

W201 defrost flap mod (vacuum element 0008008775)
 

I was searching for the vacuum element for my defrost flap and apparently they are no longer available. Came across this thread and saw one of our members (maybe even more) are having the same issue. I did find a few sites which had them priced between $80 - $150, but even those sites had zero in stock. So I decided to find an alternative method....modification. Things you will need:

w201 heater control valve (P/N 0008305784)
2 push pins from w201 glove box (P/N 1239900092)
a suitable size circlip
small joining link (I used the brass piece from the power distributor block)
check valve (P/N 0021408460)
super glue

There are 2 vacuum lines that control the defrost flap: a red/white stripe and a red/blue stripe. Plug the red/blue vacuum line with the check valve to prevent it from drawing in vacuum as you will not need this line. Disassemble the heater valve so it looks like the one in the attached photo. Next add the small joing link to the end of the disassembled valve and use the push pin to attach the two. Super glue this end so that the joining link does not move (see photo). Next, affix the circlip around the base of the valve like in the photo. Angle it a bit so that when you slide it on to the 2 protruding posts on the heater core box it fixes into place. Next, align the defrost lever end to the other end of the joining link and use the second push pin to join them together. Be sure that the defrost lever and joining link end can rotate freely. Next plug the red/white stripe vacuum line to the vacuum port on the heater valve and test.
See link below for video:
https://photos.app.goo.gl/YopQPrhAdfcQ8jUG6