Personally, I like the term “Rothbardian.” Either that, or Market Anarchist. I think the term “capitalist” has become corrupted by people thinking that capitalism is corporatism, based on how the far-left and far-right advertises anti-capitalism by blaming it for things that it was never responsable. And Voluntaryism is too liable to be labelled through much more ridiculous accusations.
Glad to see that my idea was received favorably. I agree that “ad-hoc productionist” is literally suitable and untainted.