I've heard of animal care services which provide assistance to low-income families with pets. How can I find them?

My dog is acting quite sluggish and limping around painfully (I think it might be all the salt on the ground irritating her paws). She also seems to be smacking her lips and licking them a lot, which I have read is a sign of illness. In any case, I’d like to take her to a vet and get a full checkup. My mother is receiving public assistance in the form of SSI and Medicaid. I’ve been told that there are vets or services that provide financial assistance if you meet these requirements.

Google searches have not been helpful. I’ve contacted the ASPCA, SAVE, AAHA, AVMA and United Animals Nations, but they either don’t provide services beyond spaying/neutering, can only be contacted by vets or are closed for the holidays.

I’d really like to take my dog to the vet today, but to be perfectly honest, my mother doesn’t have the cash to cover it right now. Sometime next week, perhaps, but not at the moment. How can I find a vet or an animal clinic that provides financial help to those on public assistance?