I met a fellow that used this rack on his W123 sedan:

https://www.prolineracks.com/proline-gmr165-rain-gutter-racks.html?fbclid=IwAR2udJyMtTGRhMkOaEu2EOcgTpi0QuYUPL_JsKvJ6nTJ3kPx0m-xg_w1AOQ

I cannot verify myself how it would fit on a coupe.