Microsoft Sidewinder X6 keyboard turns your Number Pad into a macro pad so you can assign any Key Combos to them. There is an extra "Calculator Key" you can assign a macro for 19 total plus you can also move it to the left side of the keyboard if you so desire.

I think they can be had for under 50 bucks. I like mine ok, not perfect for the way I want to play but if you love the Num pad I think it would be great for you.