Yes, I know. It's not exactly a Canon lens, but I couldn't find a Sigma forum. A friend has been having trouble with the lens lock on her Sigma 50-500 (also known as the Bigma). Now, the lock has jammed completely. The lens is no longer under warranty. She thinks it will be easy to fix herself. "Just two screws," she said. The problem is finding a replacement part. My first instinct would be to call Sigma. Anyone know of another place where she might order this little goodie?