I would like to know this too..if this even exists. Can be quite an eyesore right there in the engine bay.
I found a simulated cover
http://www.corvette-paragon.com/p-353268-simulated-battery-cover.aspx
Paragon also has a battery but no pic of it, not sure if it's correct:
http://www.corvette-paragon.com/p-357099-delco-hd-dc12rev588-maintenance-free-battery.aspx