Post on Craigslist and you should be able to find some. Also, the feedstores in small towns around you probably carry bales of straw. Lots of horse people use straw.
It's springtime and lots of people use straw for mulch, so call Lowe's or Home Depot and ask them if they have bales of straw, and if they don't ask if they know where you can find some. sometimes the people on the phone are more knowing than you think but won't volunteer the info unless asked .