Pity you don't want any mods.
I've just swapped a couple of casual PM's with a fellow in Nova Scotia who is considering selling his Z4M. As the Service manager for an Audi dealership, he was authorized by Roman to install an ESS supercharger. He's done a few other things as well.... Just a passing acquaintance, but it might be a lead if you change your mind. Shipping is relatively cheap. Or fly out and drive it home.