We lucked out and found a black plastic cat with light-up eyes in a
craft store bargain bin for about $1, which we used to make a light-up face.
If you can find one, cut the face off with the hacksaw, being careful not to
damage much of the internal wiring. I extended the wiring so I could attach
the switch and battery pack to the frame, cutting the existing wires and
patching in some wire with alligator clips on the ends, then wrapping it in
electrical tape to secure.
I also bypassed the existing switch and added a clicky switch from the hardware store. Remember, there should be three wires: from the eyes to the switch, from the switch to the battery, and from the battery to the eyes. Make use of the existing wiring to make your job easier.
If you can't find a black plastic cat with light-up eyes in your local craft
store, or if they've just run out, you can probably construct a bat face pretty easily out of felt and foam. Maybe even add some throwies
The bat wings are cut freehand out of thick black foam from a craft store,
reinforced with pipe cleaners glue-gunned to the back.
At first we tried gluing the wings and head to a piece of braided
elastic, but the glue kept giving way, so the tie is actually duct taped right onto
the neck of the puppet.
If I'd considered it, I would have taken advantage of the hollow pipes and snaked the wiring through the inside of the frame to protect it from snags and make the whole thing look a lot cleaner.