I personally use a Zboard Merc, absolutely could not use another keyboard after having used it. Pretty much provides you with the 1 through the - key easily accessible. Also alt, ctrl, and shift modifiers are very close in addition to your standard r, t, f, g etc keys. Warning, playing on a normal keyboard after this one will feel extremely weird, but I do HIGHLY recommend it. Especially for the amount of keybinds needed in this game.
Screenshot here
http://gearmedia.ign.com/gear/image/article/705/705398/ideazon-zboard-merc-20060505050436310-000.jpg