At the local feed store, a packet of copper sulfate was only $4.95, but I know about money constraints, trust me. No food for a couple days and you could put some unfiltered ACV in the water if you can't get the other stuff, only about a couple teaspoons to a gallon. Then fresh water and plain no-sugar yogurt for a day, then add mild stuff like scrambled eggs with the yogurt, all the while massaging the crop carefully. I've lost hens to sour crop when it got bad really fast, one from throwing up and aspirating something.