On a related note, although I own a BMW oil filter wrench, I've begun using Fram and other aftermarket filters, few of which the BMW wrench fits.
At a Checker Auto I picked a cheap plastic wrench that fits the aftermarket filters that the BMW wrench doesn't fit, but it was too thick-walled to fit into the K-bike's oil filter recess.
So when I got home, I rigged up a mandrel so that I could chuck the wrench in my drill press. While spinning the wrench at low speed in the drill press, I used a rasp to remove material from the outside of the wrench until it was the same outside diameter as the BMW wrench. Still plenty of thickness for strength. Then I switched to progressively finer grades of sandpaper on the spinning wrench until a smooth, matte finish remained.
I now have a filter wrench that fits aftermarket filters available everywhere, is light enough to pack in the bike tool kit on trips, and is cheap and easily replaceable in case I lose it.