Keva planks are a "super toy" anyway - this was just one more way to incorporate them into learning. Happy multiplication!
Keva Source: http://www.amazon.com/MindWare-44156W-KEVA-Contraptions/dp/B002V7YBNC/ref=sr_1_1?ie=UTF8&qid=1316456568&sr=8-1
This is the most cost effective way to purchase them. For some reason this set is cheaper per block and comes with the added bonuses.