You could find the chromosomes of the alternative accession numbers (NT_... / NW_...) in this directory.
Download the files with the name :
Once you download them, you might be prompted to enter some 'Keychain Access' password. The workaround which I found for this is that to convert the downloaded file to a '.txt' format and you'll be able to view whats inside the file.
An extract from the file is given below :
Chromosome RefSeq Accession.version
Reference : This article.