OK, I figured it was a long shot but worth a try. Good to know those lamps are different. I suppose with the correct size hole saw, it would be relatively easy to knock out a hole for the round version (or find someone with a knock-out tool).
I was under the impression that model I linked wasn't a CHMSL, but obviously if the LED fog units are photometrically different any stop+turn model would be inappropriate. I've seen a lot of cargo trailers out there that have a bar type light that I linked to for their rear stop+turn lamps, so I thought maybe something in that realm would work.
Are there specific requirements for the lateral mounting of the light on the rear other than "on the driver's side"? I know there are height restrictions (minimum/maximum), but the only flat-ish spot on my rear bumper is probably about 18" from my license plate. It would be technically on the driver's side, but not far off center.
Edit: My main concern regarding a too-bright rear fog is from the people with cars like Mercedes and Saab that drive on clear highways with their fog lights on (because they can see better!), which also activates their rear fog lamps. Those things are no fun being behind--in clear weather. I won't be doing that, but I have been in need of a rear fog light more than once.