Where would I go about picking up a Mule? Lurk in the Knife Exchange?
That would be a good start.
The Spyderco Mules have been made in a variety of steels, these short runs come without handles and are designed as a test bed for some of the newer blade materials.
The generic design of the Mule has proven to be a fine fixed blade for EDC, and the variety of steels available have given many of us a chance to test blades with similar design and geometry made of different alloys.
Buy a set of scales and a handful of Mules and you have a very good set-up to test the actual steels offered.
I have found that the M4 mule is a perfect EDC for me, a tough knife with excellent edge retention.
It's the knife I chose when I know my blade will be in contact with substrates like steel, iron and concrete, task that dull most steels in short order, and it's not unusual for me to encounter such materials as a consultant in the corrosion control industry.
It's true that most of my Spyderco's are folders, but my Spyderco fixed blades are up to the tough tasks I subject them to.
Big Mike