Gaming

I'd suggest grabbing it directly from the source. The ROM is continually being updated; they're on v1.2 now and actively making bug fix releases. The sensible approach is to find the file using a PC web browser's dev tools (Ctrl+Shift+I on Firefox, Chrome or Edge). This will open up a sidebar in your browser with some semi-complicated stuff meant for web developers. Find the Network tab along the top and click on it. If it's not visible as soon as you open the dev tools, you may need to scroll the tabs with a button that looks like 》 or similar, or you could click and drag the separator to increase the size of the entire sidebar.

The network tab will populate with every web request that your current tab makes. So now navigate to https://grimacesbirthday.com/ (or hit the reload button if you're already there) and watch the list fill up. In that list will be your ROM, looking something like the attached image. The ROM is just over 1 MB, probably the largest download you'll see in the list. You should be able to right click on that request and copy the URL, open it in a new tab, etc. to initiate a download of the file to your PC.

The address has changed between releases, so it may not be exactly what I showed in my screenshot.