I've heard people sell them on Ebay,ya might try there.
Can ya fly in a day early? If you can get them for Fri.Oct29 and celebrate early!
If that doesn't work on Halloween night and your 37th birthday you could have a nice dinner at one of the restaurants at the Boardwalk or Y&B ,then stroll the Boardwalk after dinner.Y'all will be able to Trick or Treat and enjoy the activities there...ya know streeeeeetch the birthday/Halloween celebration out longer! You'll still have fun...after all you're at WDW!!!