My source:

http://tinyurl.com/5cj2tp

$51.99 for a 50 pound sack of Star-Dri 100 Malto- DE of 10

Shipping $4.49

Pure Karbolyn is around $50 for 4.4 pounds. Haven't tried it but I'd
assume it'd work well. Probably something I'd use for races but not
for training.

I usually dump some malto in with my favorite electrolyte powder (Heed
or Cytomax depending on mood).

Works for me. But... always try your own and see what works.
Speaking from experience, try it on a training ride as you do not want
to go into "gastric distress" during a race.

T. Kenji Sugahara
Executive Director
Oregon Bicycle Racing Association
503-302-4935