Also you could check to see if your grocery store has any scraps from produce or anything they could donate. I used to work in produce and we threw away anything with a dent or bruise or a slight bad spot in it. I would be careful about using anything that has a fungus on it, but perhaps you could get some greens and cut off any bad part. It is worth a shot to ask!
Keep an eye for any sales of produce, and I agree that inexpensive bags of frozen veggies as well as chicken breast won't run you to the ground. I do hope that you will make sure they have a calcium supplement though, because this is of upmost importance, especially when you can't necessarily pick out fruits and veggies with the right ratios.
I think we all understand about finances, and I know I would happily go without eating to provide for my gliders and my cat. Take this time to make handmade toys or use simple things like bottle caps and the like instead of shopping at a pet store.