When I bought the car the driver's seat height adjustment mechanism was frozen and the socket on the plastic lever was broken. I got the mechanism oiled and freed up but I was not ready to pay $40 for a new, flimsy lever... so I decided to fix the old one. I cut a strip of aluminum and JB Welded it to the socket. I used safety wire to make sure that that I got a good bond.
A bolt replaced the pin that was broken off.
Initial tests indicate that the lever is as good as new... or better.
Updated January 2023...
The repair described above seems to be fine, I almost never use the lever since I am normally the only person who drives the car.
When I bought my 2000 S the driver's seat had the same problem, so I did the same repair. On this car the pin that centers the lever on the receiver in the seat was present, so initially I tried the repaired lever with the pin in place. Unfortunately the splines on the lever and the receiver were too damaged and the lever slipped as soon as significant pressure was put on it. So I removed the pin, drilled out the hole to 3/16" and inserted a bolt. The bolt holds the two pieces together solidly and now it doesn't slip.