Forgot to leave a update here. Tried to find the source code for the page linked in the above post, but couldn't. Given it wasn't minified, I just imported it into Github ( https://github.com/ipfs/public-gateway-checker ) so we could host it on Github Pages (in case the gateway stopped working for whatever reason).
If you come across new public gateways, a PR with adding it to the list, would be greatly appreciated!
Thanks @cbluth for the addition of the macholibre gateway!