Mack key blanks

This is a rather simple thing, or so I thought, but can anyone tell me what key blanks work to duplicate modern Mack keys? I just bought a 2000 CX613 on Tuesday and want to make a few copies of the key. My local hardware store always has been able to copy my Freightliner, International, and KW keys but they just got one of them automated machines and couldn't find a blank that would work. They told me if I could find a key blank number they could order them and make my copies. I sure don't want to have to order on from the dealer like I have to with my Volvo VNM42 which has the special laser cut key which was $100 last time I ordered one!

Thanks for the help, I am sure this is only the first of many questions since I have not owned a Mack before and the last one I drove was a mid 80's R model dump truck for my dad.

 

I thought they were simple, my dad's trucks were the same as a toolbox or lawn mower, so I thought this one would be also. Maybe the store just needs to practice with the new machine, they only have had it for a few weeks. Thanks for your quick reply.