I don't know of any other low cost places to look...except for checking around at local feral rescue groups and see who they use to spay. I know most feral rescue groups have some kind of low cost spay worked out due to the number of cats they catch, alter and release.

the only reason why I didn't wait to have Scout fixed was I was worried about him spraying. I don't know much about females in heat...but I don't know if it would necessarily hurt her to wait til January if you can't afford it now. As long as she doesn't go outside and isn't around other male cats..I don't think it would be a problem...Someone please correct me if I'm wrong.

Have you called different vets to get a price? Of all the vets around here, the highest was $243 and the lowest was already my current vet at $70. Good Luck!