wow, that's a pretty good price!
if you're building 2s or 3s packs, you can get the balance taps
from a123. horizon hobby is an authorized a123 dealer, but surprisingly they don't have the taps.
if you want 4s or higher, i would imagine you could use any other balance tap that would match the charger/balancer you use (i have a123's balancer/charger, which will only balance up to 3s).
MetalMan has a great thread on how to build a123 packs from dewalt packs.