Any cylinder with a 24" diameter would do it. Double sticky tape a piece of sandpaper on it and sand away. The plant should not even be bothered with...
How do you adapt a "one handed clamp to it"..... I'm getting ideas as I type - but if you've already got it down I'd love to see how you actually do...
Here's a vid that might be relevant to your situation. I thought I had this going on with a 40 year old Acoustic. It turned out to be something else...