State map pendants have been popular for a while. Very likely because celebrities have been spotted wearing them. You can make your own out of wire. See how Julieta of VJuliet does it.
I am guessing she used 20G wire. Remember to work harden (set the shape) by hammering lightly with a nylon hammer. If you want to get a flattened look, go ahead and hammer with something stronger like a chasing hammer.