I've seen a video of how to make your own custom board especially for quilters (sorry I can't remember if it was on here or YouTube). The person did what others have suggested and got a piece of plywood the desired size and some bolts from the hardware store. Their new piece of plywood has padding put on it, people here have suggested insul bright but people I know (including Ricky Tims at one of his seminars) have suggested going to the thrift store and getting one of the wool (often grey) army surplus style blankets. several layers of this go onto the board and top it off with good quality drill cotton. Attach it to the back of the plywood with heavy duty staple gun or upholstery tacks. Lay it on the floor padded side down. Take your current ironing board and remove the cover and any padding, turn it upside down and put it on top of your new custom made top (so the top of the metal ironing board will be facing the back of your new plywood top). Take the bolts that you purchased with the plywood and screw them through the metal of your old ironing board into the back of your new custom top (you may be able to use existing holes in the ironing board or you may need to enlarge them).
At the end of the process you will have your own great custom made ironing board top that's nice and flat, but still able to be folded up if necessary.
If I find the video, I will post a link so all of this makes more sense
