There's Ohlins - then there's all the rest.
Model BM-420 - Fits 94+ K1100s (Won't work on 93 and earlier models because the reservoir would hit the rear ABS modulator. If your ABS has been removed then you could use the BM-240
There's also one that has both reservoirs remotely mounted (I have one on my 93 K1100LT) but I don't know the model number of that one.
Model S46PR1C1S or BM137/46PCRS - Fits non-ABS K75 and 2-valve K100 models. (Again, the issue is the rear ABS modulator and the shock reservoir wanting to occupy the same space.)
Model BM847/HRCS - Fits ABS K75s and 2 valve K100s. On this one the reservoir is mounted to the rear to accommodate the ABS modulator.
Progressive Suspension also makes two models of shocks for K75s and 2 valve K100s. They're a decent shock and, though not the best, a darn sight better than the stock shocks on those bikes.
Hagen used to make shocks for BMWs too but I don't think the company is around anymore.
Fox Shocks made "twin-clicker" shocks for both 2 valve and 4 valve K bikes which are a pretty good shock but I think they've moved on are out of production on those. You can find them occasionally on Fleabay.