rebuilding the harness yourself is the way to go. There are probably places in Germany that sell rebuilt harnesses but that will be quite pricey. If you don't want to do it, any auto electrical shop should be able to fix it for you

many other cars of the era use L jet especially BMWs ... try your junkyard for some good parts and get a good soldering iron!

make sure to change all the hoses in there with the correct FI hose and clamps. Fires are not fun!