Rotating books and sheet music on my music stand made it hard to leave my pencil and other accessories on its lip. My local music store had this Manhasset Accessory Shelf for $4 so I picked it up. I should have gotten one a long time ago.
That mini-boom microphone holder in the photo is by On-Stage Stands. It has a screw-clamp that won't damage your stand's finish. It sells for less than $15.