I think all the new ones must come from the same OEM (they all look like the same thing anyhow) and have a ABS rubber/plastic backing instead of the cardboard/foamcore, and a different padding material. They look like they'll hold up pretty good over time.
At this point I'd go ahead and replace it altogether. The padding and backing are probably getting shot and even if you recover it it will probably start getting all moldy and nasty behind it. That original foam padding starts getting all hard and crumbly and it won't take the glue right (or it will and just comes off the backing along with the fabric anyway!)
I got mine from 1aauto, but like I said I think they're all the same and from what I found researching mine all cost roughly the same.