I was brainstorming about the problem with my roommate and came up with a simple but probably very effective solution!
I am planning to take a clear sheet of plastic, like the ones used on overhead projectors for presentations, and cutting some strips the width and length of the M9 blade. Then I will put one strip on each side of the blade and then slide it into the scabbard. The plastic strips are totally smooth so they don't cause any wear on the blades and they don't absorb any oil. Because of the stiffness of the strips they also can't get stuck at the bottom of the scabbard.
Seems like a good idea, so I am going to try it over the weekend.
I will let you know what the results are
Best regards,
Menno
The Netherlands