Saw this on eBay today, for anyone who needs this gasket. I didn't check the part number, but the profile of the gasket certainly looks like the one that fits on the chassis and seals against the rear of the hood when it closes.
Not mine, no affiliation.
http://www.ebay.com/itm/BMW-2800-3-...ash=item3f6ceaf698:g:cJ8AAOSwh2xX~cgw&vxp=mtr
Not mine, no affiliation.
http://www.ebay.com/itm/BMW-2800-3-...ash=item3f6ceaf698:g:cJ8AAOSwh2xX~cgw&vxp=mtr