O.k... $.02 more.... I also needed a wider music stand on my keyboards. So, on the Yamaha & the Korg, here's what I did. I had an old piece of plastic floor protector (the kind of mat that goes underneath a wheeled desk chair to protect the carpet). I cut it into 2 pieces about 1 foot high by 2 feet wide (actually a bit wider, I think). I used a jigsaw and it cut very easily. I also rounded off the top corners of the plastic. It sands very easily.
Then I took 2 pieces of scrap wood trim - the kind that is usually used to frame a door - and cut them to the same width as the new racks. I spray painted all the items - the Yamaha ones black and the Korg ones gray. I ran velcro strips on the flat part of the existing music rack for the Yamaha and on the bottom of the wood trim piece and stuck the wood in the space where the music usually sits. Since the wood has an angle to it, it's higher in front than in back which keeps the music from falling forward. It looks & works really good. On the Korg, I didn't even bother with the Velcro. Everything just happened to sit just right without it. Now I have music racks that hold 3+ sheets open at a time, and still looks pretty nice.