I spoke with a very nice and knowledgable fellow named John at the Classic Center and he said he has been in the MB parts game since 1975 and this was the first time anyone had asked for that part (he knew just what I was talking about). It is no longer available.
I was very careful and pried the two halves apart and could reuse them.
Now, any tips for getting the new skins on? Are the horsehair foundations still available or are they now synthetic? About what should I expect to pay for new foundations? Any good experiences with suppliers?