Thought I'd pass along a success on replacing the entire 8700c housing. I had my BB for a year without ever dropping it, then within a week, forgot to buckle it back in my belt case and had it crash on the sidewalk two times!
For $35 shipped, I picked up the entire housing at
Cellular Nationwide Network. They also sell the individual parts (speaker, lens with or without Cingular logo).
I received the casing about a week after ordering (shipped from Hong Kong). It was securely packaged, and had all the original protective film over the lens (both inside around the gasket as well as on the outside). Manufacturing marks are identical to the original case, so it is indeed an OEM case.
The only omission to the instructions on this thread are to transfer the speaker and microphone from the front part of the housing. The microphone just needs to be gently pried up from the edge, and presses right down in the new housing.
Using latex gloves will ensure you don't get any smudges or dust on the electronics, and make sure you don't use too small a screwdriver to pry the rear clips during removal.
My new housing actually gives me a better overall fit than the original (old one had some creaking on teh upper right corner, though that might have been fixed by tightening the screw for that area).