Well, it does have bag loops so that is a nice place to start.
Are you talking about a support for a large bag? If so, I found a support that loops around the seat stays and provides a base for the bottom of the bag. Not exceptionally classy, but a practical way to get the job done. I found mine at a Yard Sale and it took me over a year to figure out how to use the thing. Unfortunately the only pictures I have are of it under the bag. The portion which contacts the frame has a plastic coating on the chrome frame.