By the way there are blank dice sold, copy the markings from the set on a printer that can print clear decals, or hand write them, paint the dice.
May be cheaper than buying them, unless you dont care about paying $1 per dice, which isn't bad, but looking at the supplemental set for $12.95 you don't get enough dice to make a big pool, (read the set list and you will be surprised that its nothing compared to what you get in the main box)
if you bought that set yo would still need to borrow from the GM, i'd imagine you need a couple sets, which will get pricey.
With the make your own option you can get the dice you want based on your characters needs.