Try GBodyParts.
They have one. Look under Monte Carlo SS on their web sight, I believe it's the same as the GN's. ( I think American Cushion Co. makes it )
Beware kinda pricey !!!
I would like to replace mine also but the $$$$ thing is what's holding me up.
I think it gives you the option to buy just the bottom and save a few bucks, not much though. I don't need the whole thing either, but for the difference in price you mind as well get the whole thing.