Thanks for the link, most appreciated, but most of the valves for different models seem to have straight through piping whereas the Supra valve pipe enters one end and exits at a right angle.
I'm not sure how easy it will be, if at all, to adapt another Toyota model's heater valve to fit the Supra not having the luxury of time to fiddle around, especially when the dash is out and not being able to test it properly until all the dash is back in again. Not a two minute job.
I would've thought some of the Lexus models such as the mid nineties GS300 would have shared the same part but no they don't.
My gut feeling is the MK4 Supra heater valve is specific to this model only.