Man I was looking for that stuff, but I had no luck finding it. Did you find it in a store?
By the way, I scrapped the Bondo idea. Actually, it scrapped itself. As I began to sand it, as the plastic flexed the Bondo just popped clean off the styrene. It came off easily so I started using Squadron Putty, which I found at my local hobby shop. It says that it adheres to styrene best, and is easy to sand and leaves a good finish, so I'll try that out.