I asked the same question about a year ago. Someone told me Wizard in Havazoo made one, but it was around $700.00. I sent Wizard an email, but they didn't reply. I spoke to their rep at the LA Boat Show and he told me they made one or two, but the cost was to high and there wasn't a large enough market to justify the cost of fabrication.
Whipple Industries makes a cool polished stainless cover. Don't know what the cost is but check out their web site for some pics.