Have never seen one and I love Cotinus so am always looking. I do have one that I bought as 'Royal Purple' and is 12 years old and barely 5' tall. It is in terrible soil and may have bonsai'd itself due to rocky ground below shallow layer of topsoil. Or it is a mutation...either way it won't do you much good.

I find propagations I buy as 'Royal Purple' to be slow-growing also. I am not aware of any dwarf cultivars, what are these called?

There is a green-leaved variety called 'Young Lady' that is supposed to be dwarf (or dwarf-ish) with a 4-6' height rather than the 15-20' on most of the others, with all of the usual warnings about woody plant growth....

I have a 'Young Lady' but have not had it long enough to assess its growth rate. Stay tuned!

I know about that one, I do not remember it being stated explicitly that it is dwarf. Understated growth potential is common, there is a fear of scaring people off so plant after plant is misrepresented by commercial sources, with sizes acheived after short periods of time being called "mature" etc.

'Ancot' was also described as smaller growing, I was seeing specimens above head height in plantings here quite soon after it came on the local market.

It doesn't state 'dwarf' but the height is listed as 4'. Now we all know how useful that information is! However that is far lower than any other Cotinus I have seen and I don't remember 'Ancot' being listed as vastly different from the purple cultivars (at least the way I placed it tells me that). Time will tell!