Meadow Mist, I have the big board like in the link Rhonda posted and didn't want to pay that price for a new cover. I buy the canvas fabric in the Home Dec dept from Joann's and make a new cover when I need one. The canvas generally comes 57-60 inches wide so you may not need a lot of yardage. You can use the cover you currently have on it as a "pattern". It is simple to make if you only make it as long and narrow as your board without the hinge factor in the short end. I use the drawstring method and it bunches up a bit underneath, but I don't iron on that area anyway.....lol
On a side note to anyone reading this, have any of you used the drop cloths from Harbor Freight as an ironing board cover? I haven't bought one but the machine embroidery folks seem to like them.