You might post this in the regular section too since you're really not selling or buying anything.
Have you contacted feed companies? If it's for a project for school, they probably have old ones laying around gathering dust. Check into the major comanies & also local dealers.
Have you checked with your local arena that might host rodeos or big horse shows. They usually give them away after events. Many a rancher around my area has a tarp on top of his haystack that reads......Coors Light presents.......!