If you're talking about the backplate that attaches to the back of the case, graphics cards generally come with that, and the ones that are low profile compatible often come with a low profile backplate that you can switch in. If you're talking about a backplate for mounting a waterblock to the gpu, that waterblock should include an appropriate backplate.
The MSI Lightning 7970, Sapphire Vapor-X Ghz Edition 7970, and PowerColor PCS+ 7970 all have backplates as well. I think the ASUS DCUII card does too but I'm guessing if you don't want the Matrix card you also don't want the DCUII.
The vapor x ghz doesnt have a backplate, I just checked on newegg, and both the cards I looked at neither had backplates
Thats what im goin to do, tax money should be here soon. Is the lightning a beast? How well does it oc? I was goin to just build a whole new rig and sell this one I have, but the only thing this rig is missing is a strong gpu and I need a cpu cooler.