Replacing all of the wire harnesses with new ones is going to cost a lot. Look at the diagram linked to below and determine which one burned up. Click on the 5 digit number by it and it'll take you to a page with Toyota part numbers. Call a Toyota dealership and have them look up the part number and make sure that it's even still available. If it is you can usually get them for less from toyotaworld.com. The remaining options are: fix it or buy a used one from someone.
http://www.cygnusx1.net/Supra/Librar...spx?F=8202&P=2