If there are any neon sign makers close to you try and see if you can get some of the high voltage wire they use. Also if you might check with any electricians that do high voltage work, some of the instrumentation wire used there would probably work.
Be sure you tell them what you need it for, they could know of something else that might work. They might even donate some short pieces to you, and Donuts always help to put/keep the wheels in motion.
Don