I found this tool - uif2iso. It's a tiny little file that you have to build from source (instructions for building anything from source are here). After you've built it and installed it, just run these commands in the directory in which you installed uif2iso.
sudo uif2iso path/to/uif/file.uif path/for/iso/file.isoIt's really that easy - just input the location of the .uif, then space, then output where you what the new iso file to be placed and named.
It took about 3 minutes to convert 4.7GB for me. Just make sure you keep the terminal window open.