Same here. I named mine Lefty and he is my favorite orc of them all! My coworker suggested that I should give him a hook hand.
Get a fish hook, or make a hook from a bent paperclip or piece of wire, and pliers. To add a little safety to it, dip the sharp end in glue and let dry until less dangerous. You may need to do this a few times.
With a push pin, push a hole into the arm. The plastic is hard, so you may end up needing a handheld non-electric drill, available under ten bucks at a hobby store.
Use a pliers to cut the fish hook to the right length and insert. You may need superglue. You'll find the drill useful for any pre-assembled mini's that weren't glued properly.