Actually, I hit up the Autopower website....
I'm a little affeared of their "street" roll bars, but at least they say they're just for loooks... The "race" roll bars look like they're not too bad. (And their Spec Miata cage looks downright decent.) Just don't get the one with the bolt-in cross support. Go welded all the way!
http://www.autopowerindustries.com/rollbars.asp