Someone here in Chicago rigged up a bracket that didn't require them to drill holes in the bumper. I'm sure they or someone here who knows them will chime in.

Buying the part from the dealer isn't a bad option. That's where I got mine, but I made the dealer pay for it as it SHOULD come with the car in a state where it is required (like it is here). I didn't mount it, I just keep it in the trunk with the idea that if I ever get pulled over for it, I will tell the cop I just finally got it from the dealer today and am going to install it when I get home. That should work at least once.