2mm leads are easy to find -- they are standard for draftsmen. And you can get them in colors, too. As for the others: The Palomino Blackwings
The Staedtler Noricas
The Staedtler all-graphites were about a dollar each.
I might add that for my workshop, I have recently bought some 5.6mm mechanical pencils, which are also easy to find on Amazon.