I believe rocker panels are F classed at the dealershipt (discontinued) and last I heard you can still get the body trim at the dealership ($$$) IMO try contacting Jeff Watson at Champion Toyota to see what he can get them for you at.
For a simplified version of things, since it can get confusing, this is a dealereship in Houston that is just down the road from a major Toyota parts distributorship, so no shipping charges to the dealership. Jeff Watson is a parts salesman there that decided to specialize in Supras early in the internet era, 10 years ago (back when we were all on SOGI). At the time, it was called Jay Marks Toyota, and is now Champion Toyota, but it is also known as Toyota World. The contact details are at http://toyotaworld.com/ Call and ask for Jeff, and you will get a discount even if he isn't available to take your call. 800-327-2087 But for details, talk to Jeff, he knows Supras and Jay Marks/Champion/Toyotaworld is a major supporter of our various Supra events.
Since you have a MK II, you should also check out the Restoration forums at http://www.celicasupra.com There was talk recently of replacement quarterpanels out of Quebec.