I replaced my passenger side maroon door molding 3 years ago and it cost $172 delivered.
Those parts are drying up. I did a search and found a possible lead.
Try EB Toyota Parts North Attleborough, MA They had blue ones for $147. You need the Part numbers for grey metallic Left and right in your case.
parts-bochtoyotasouth@emails.revolutionparts.com 1-866-574-2624
http://toyotaparts.bochtoyotasouth.com/
Once you have the part numbers Try a search at oemparters. They list all the dealerships for a part by price and location.
http://oemparter.com/us_toyota_supra_1986-1988/
Some 86 1/2 to 88 owners have replaced all their belts with 89-92 ones that don't rust out.
What I did with my old style metal backed one was to seal the exposed painted metal to the rubber edges with a thin layer of silicone and let it dry before installing to prevent water from rusting it out like before. I also did some of the others on the car that way except the large curved rear ones. Be aware that the door moldings have a 10mm nut in front and push in pop holders along the length. There is also 2 strips of tape that needs the paper pulled off when installing. Make sure the contact surfaces are clean on the door or the tape won't stick well.
Good Luck