If you haven't already, you may want to go ahead and list him on Adopt-a-pet. It lets individuals as well as shelters list animals for adoption, and has some tools to help with adoption screening. https://rehome.adoptapet.com/
As far as his medical costs go, it sounds like you have a group of folks who are invested in him, but money is still tight. Have you considered running an online fundraiser through GoFundMe or even just using a Paypal/Venmo account? If you can get half a dozen people to give you $10 each, that would at least let you get him vaccinated through one of the clinics. Doing it as a step-by-step process might be the best option right now, until you find a local group that can help.
#FosteringaPet