Honestly, I'm a little peeved at your feed store on your behalf. They should be offering to order more if you're offering to buy it.
Even offer to "pre-pay" ...
If local doesn't want to supply ... just plan a trip to "town" ... stock up a month or two of feed ... if you need to "justify" your trip, just go shopping at a store you don't have local, or go out to eat ... yesterday I drove 100 miles one way to my dentist ... while in Tucson ... I did spend some other money since I was there ... just make a list.