Any sheet metal shop shoul;d be able to fab that up from scratch for you. It shouldn't be that big of a deal. Just tell them how much of a Z you need on it.
You can also buy a semi-finished SB Plate for a wider frame than you have and get the sheet metal shop to just make it to be offset like the one you want. You are just talking about 4 bends at a 45 deg angle. Then fit the rest to your car. It does look cool though.
Ed