Don't know if it is the one you're trying to find but Niche Gardens in Chapel
Hill, NC (www.nichegdn.com) has a yellow flame azalea. (and they do mail
order!)

We inherited a "up to the gutters" flame azalea when we bought our house. I've
tried several times to root cuttings but no luck. Planning to try layering it
to see what might happen.

Marcy