Porsche used Hella 139 fog lights with mounts in the center of the back.They are hard to find and cost around $1,000 when you can find a set. These, with top/bottom mounts, were used on Mercedes and a number of other marques. Other than the position of the mounts, these are identical to the ones used by Hella.
It wouldn't be that difficult to modify either these or your LWB in order for them to fit. My thinking is that it would be relatively easy to simply remove the riveted mounts and reattach them on the back. Everything will look identical to the Porsche/Hella lamps from the front.
One Set Only
You will find the correct Best-in-Class Hella 139 fog lights HERE. Not always available.