I would prefer not to use nigralisto, which I assume but cannot confirm is the Esperanto term for 'blacklist'.
Mi proponas bojkotlisto. Bojkoto estas bona esperanto vorto kaj internacia komprenebla.
Nigra listo (note, two words) is an established expression in Esperanto. (It's in PIV, anyway.) Of course, that doesn't mean you can't suggest an alternative.
I would probably use something like:
Listo da evitindaj vendejoj
But if you are looking for a single word, I cannot think of any decent one, as I think evitindvendejlisto sounds too weird. :)
Perhaps sankcio listo, a direct translation of "sanction list", which is a list of entities with whom you're prohibited from doing business with, by law.
Depending on the context, though, that might be too strong of a term.
I think nigralisto as a single-word description is quite good, because its equivalent "blacklist" or literal transcription is widely spread in different languages, especially in computer-connected topics. Also it can be not only black-for-buying list, it's a bit more common. If to use full description - better use variant of Lyubomir Vasilev.