I wanted something a bit higher (as our cars are so short), so I picked up a strip of red LED lights and an aluminum channel for them to go in, and bent the housing to the curve of the rear windscreen.

https://www.superbrightleds.com/cat/accent-lighting-led-module-strings/

It's narrow, bright and at the top of my rear glass to make it more visible - I've routed the wire to come down from the headliner (as I had the headliner out when I installed it).  Took me some time to find a glue to hold it in place, but finally settled on some strong double sided tape which has done the job for 3 years.

Scott

   

Fog lamp.

Just get a common or garden fog lamp as fitted from around 1980 onwards and mount it upside down on the rearf parcel shelf.  

Looks factory, works well.

Most excellent! Thanks for the ideas and links fellas. 

The Hella is a good product, not a Chinese el-cheapo. I think they're made in New Zealand.
I got mine from here>>> //www.danielsternlighting.com/products/products.html
Pretty sure it was the Model 39, that's the least angled one. 

I got mine from Hunter classic Sports Cars. his web site is down, but he is still in business.

Also, In the past I raided junk yards, 1st gen Ford tempo/Mercury topaz worked well as i recall. The ones from Hunter were cheap and good however.

Mine would not be of much help to you.  I ordered a compact LED one years ago and thought it was too big.  I made a much smaller sheet metal enclosure for the lamps and installed that at the top of my car's rear screen.  The unit is about 1/2" tall so it does not significantly block rearward vision.

I have seen a number of people suggest using the angled Hella 3rd brake lights.  They have a black plastic housing that has an angled mounting surface covered with double-sided foam mounting tape.  They appear to be available with different angled mounting flanges to accommodate different cars.  For some off-site reading about the Hella lamps, see the link below.

https://www.bmw2002faq.com/forums/topic/105048-3rd-brake-light-consensus-hella-38/

EDIT:  I forgot to post a picture link to my 3rd brake lamp.  I cannot post a direct link but see the page below and look for the "brakelight02.jpg" file.
https://sites.google.com/site/purlawson/home/pictures

Thinking its about time to install a high mount/3rd brake light for safety sake. What is everyone using that works well?