holster
I just ordered a black flap holster (left or reverse orientation type) for my dragoon from Dixie. The Walker has a longer "mid section" and overall length, so I'm betting that it wouldn't fit in this holster.
Sounds like you are talking about the open-top one? If so, and they say that dragoons will fit, I would be comfortable in my expectation that indeed they will.
The Dragoons are very similar in size to the Walker in terms of the cylinder circumfrance and frame size - accept the mid-section and overall length is shorter. But they would be a decent fit because the trigger guard would prevent the holster from "swallowing" them.
Cabela's also has an open top holster- you may check that - they don't make any claims for the Dragoon, but it should be the same deal.