If you have a Buckeye distributor
nearby, they can order it for you.
Teddy Lancaster at Running Bear Farm
carries it, as does Sandy Terp at Neigh-Per-Say. If you're going to be at
a ride where they're setting up shop, contact them in advance so they can be
sure to have it for you. That way you'll save money on
shipping.
I've had great experience with
ordering it from Paddi at Canadian Trail House. Paddi has it drop shipped
at a very good price. (Or at least she did -- can't find any mention of
PNW on her website.)
When I order it, I get only the
20 pound tubs, and I usually get two at a time. It will keep forever, so
long as you keep it dry.