http://www.allbrands.com/products/abp00805-0711.html
There is one view on that site
if you google: big board ironing board cover you should get some help with other views.
It's basically a 22 x 59 piece of high grade plywood with three boards placed under it to keep it from sliding around the ironing board.
It came with a thin (about 1/8 inch thick) poly-type pad and a twill cover. The cover was rather skimpy. I have to put it back on the board while it's still damp and it barely makes it.
I bought mine, but I don't think it would be very hard to make one - if you know how to use a saw - and/or could get someone to make one.
I thought it was rather spendy, but I do like it. And from the amount of use I've gotten out of it, it was worth it.
Won't even go into detail on how much I've spent on stuff that isn't being used.
I think a slightly smaller model is also available.
I do a lot of cutting (with a mat, of course) on this set-up, too. Perfect height.
It makes ironing fabric so much easier !!!!!! :-)