I'm pretty sure it is a dealer only item. You may have luck finding a good used one from someone who's parting out a car though.
The part number is: 83710-14731
Just for reference here's the EPC page:
http://www.cygnusx1.net/Supra/Librar...spx?F=8301&P=3 The long part is the same for any of the transmissions, but the shorter segment(s) are different for automatic transmissions.