How do I get an SSL certificate that works on my local network? It cannot be self-signed, as this messes up AJAX calls. I haven't found an issuer that would allow me to do something like this yet.
You do not need a paid certificate for localhost.
You could make an self-signed and import it in browser certificate store. For ajax (and all other functionality) it will be absolutely correct one.
You could create such certificate with OpenSSL (command line tool) or with graphic tool as XCA on Windows OS.