smooth black Group 24 battery to use with fake retro kit?

So I'm trying to find a high CCA modern sealed battery that is black and smooth to fake a retro battery. Weskcar is now making a deluxe kit that, instead of stickers, includes side and top plates that are cast like the originals plus fake correct looking caps in various colors, but to pull it off you really need a very plain black battery case. Anybody using something like that?