The owner of one of the lumber yards in town is a fellow reloader and shooter. I asked him to start carrying bulk corncob, which he now does. A 40 pound bag is up to $15.25 a bag now. Until a month ago, it was $12.75 a bag, but fuel prices have driven it up, along with everything else.
As mentioned, get the 1/8" size corn cob. There is no way to reduce the larger corn cob. I tried a food processor, a coffee grinder and a sausage grinder, but none of them would do it.
Hope this helps.
Fred