I don't know what size it was exactly, but I saw a grey one at the Neiman Marcus in San Francisco this afternoon. It was lovely, though the chain seemed a bit long. It might have been a small one, but since I'm not familiar with the sizes, I can't say for sure. Might be worth giving them a call tomorrow to check??
I have the large and it is not that large. The medium seemed too small and for a few dollars more the large was the way to go. the large seems to be the most popular. I don't think you can fit much in the medium and the small is like a clutch with a chain.
There is a medium size 2.55 chanel (authentic) on ebay. However, he wants more than what the bag costs. The seller goes by RJC. He had a listing called something like RJC Channel Aniversary Bag. I believed he had one gray medium and a few larges.