stupid question but will any tuner lug nuts work (e.g. 12 x 1.50, 12x1.25)? i'm not exactly sure what it means by 21 hex req.
http://www.garage16.ca/SearchResults.asp?Cat=2661
Mazdas are 12x1.5. I would use some standard Muteki nuts, and the color/length is all up to you.