Did you check the link TommyCat posted?
Call YAPS back and see if they know of another organization that will help. Call any shelters/humane orgs and see if they know anyone.
If NOTHING else - will any of the vets take a payment plan? If so - maybe your sis can help out to get it started.
If it comes down to a choice, surrender Buddy to a no-kill place so he can at least get treatment.
HUGS.
(Think of what a vet will charge to put him down! Try to find a payment plan)
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