No idea where you can find steel spears, I've never found any. I just spawned one using Z just to compare it to the sting I was murdering everything with. I found the katana in a basement of a house though, on a shelf. It doesn't really compare to the wasp sting though, way too slow.
Killing a couple wasps isn't that bad, especially if you use firearms. Don't have to kill a whole nest to get a sting, might get it from the first one.
I came close to a house with a wasp, shot one that approached me with my M1911, and took its sting. Lured some more wasps to a single space window and killed 5 of them one after another without being hit using the wasp sting. The sting keeps removing moves from them on every hit due to being a spear (skewered + forced to the ground, etc), so after the first hit they can't do anything.
It's such a fast weapon, with a little weapon skill (which comes really quick just by massacreing regular zombies after getting a lil xp) you can take on zombie brutes, fast zombies, zombie necromancers - all without being hit. Even fighting multiple regular zombies at once you don't get hit, I had 3 regular zombies in my face - stabbed 1, 2, 3, then 1,2,3. First hits removed their moves, second hits killed them all. The only common monster I've found that poses a problem so far is skeletons, and they still die easy enough - you just can't push them to the ground at low skill.