In my (outdated) version of Firefox, I can type "/" to get the quick search box to show up at the bottom. If you can't, then go to edit > find or press ctrl+f in the source window that pops up. Search for "/* Cleaned CSS: */".
The section you find should look sort of like this. You want to select everything from the line under it until the line just above <style>. (Example of where to end here)
As far as I know, the only CSS that IJ marks as "Cleaned CSS" in the source is user-supplied, so that should help you avoid copying the wrong section. But that's for S2 styles. I have no idea how to make sure you grab ever part of an S1 style.