I just went to my FLGS and picked up two green d4's two yellow d8 two red d10 and two black d12. I already had two blue d6 and white d6. Cost me about $5 and I think most FLGS shoudl have a dice section that has individual dice for sale in assorted colors
Personally I think id rather use actual d4, d8s and so on rather than the d12's with modded facings which is what will be packed in the box set.