Reno, they have plastic boxes meant for steel studs (why I think the bonding lug could be integrated quite easily).
It has a metal mounting tab. The grommet provides the horizontal support, just like Romex in a bored hole. The vertical support and within 12" of the box, is usually a tywrap.
You can get mad about plastic boxes but they are cheap and fast to install (no Romex clamp screw to tighten) so I think they are just a fact now.
I am not an engineer but it only took me a minute to come up with several ways to get from the EGC to the metal mounting strap. It could be as complicated/expensive as a green ground screw in a tab that comes in the bottom of the box to a spring stab or just a metal lip over the edge of the box you could drive a ground clip on.
I do think there is already a plastic box with a bonding means but I don't have a link to it. I think I saw it mentioned on the Fl IAEI BB when this first came up but I may be wrong about that.
