Where does one pick up Boric Acid? I don't wanna end up on the FBI's watch list for ordering as much as I'd need. HA! I've been told Copper Sulfate, but I also have researched that too much will kill all of your invertebrates, which will eventually harm your entire fish population. I'm trying to save what I have, not kick off an entire fish kill while getting rid of the ankle breakers. I'm honestly scared when my dogs take off running around the ponds....
I would be tempted to try catching some first with either a Gee Crawfish Trap (they look too big for a minnow trap opening to me) or the bacon on a string trick. Might as well see if you can have a nice crawfish boil before you whack them!

If water temps are cold, they may not be active and just sitting in their burrows so trapping might not work until spring.
I haven't bought any lately, but you used to be able to buy boric acid at a drugstore pretty cheap.