Hey!
Not sure if this helps, but there are two that come to mind.
Waggle is a nonprofit that raises funds to cover veterinary bills of privately owned pets. From what I understand, if the pet owner qualifies, they would pay up front the cost, then Waggle does a sort of "gofundme" for the pet, and whatever is raised is turned over to the Vet providing the treatment. It gets auto-closed if/when the requested amount is reached.
The other organization, 15/10 foundation I don't know as much about, but they seem to be similar in crowdfunding using social media and is typically reserved for dogs only. I believe it's primarily for shelter dogs, but I've seen exceptions to that on X based on the story.
Hope these help!
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Sarah Sukhram
Vol. & Foster Coordinator
Pasco County Animal Services
Land O' Lakes, FL
https://www.pascocountyfl.net/408/Animal-Services------------------------------