I got rather bored last night, bored enough to turn part of a wire hanger I'd murdered to make a sort of receipt spike for to do items in to a belt clip for my hanger.
Making it required the hammer itself, carpenter's pincers and a drill with a 2mm bit - you could hammer in a panel pin and remove it, if you want to hammer your hammer.
I started with a straight piece and bent the angles by sliding the wire in to the hammer claw and bending for right angles.
The pincers worked well for more awkward angles, along with the claw on the handle.
I worked the shape of it out before drilling holes. One tip when bending wire shapes, work from one end to the other, don't attempt to do stuff in the middle, it's ridiculously fiddly.
Because the wire's a pressure fit I orientated the attachments to the hammer perpendicular to each other.
It works well, took about twenty minutes and because the hook sits comfortably under my palm it doesn't impede my hammering activities...