Okay, crisis averted for the time being. Thanks to my favourite local hardware supplier, Lincoln Creek Lumber in Centralia, I was able to source an improvised inline ball valve to serve as temporary emergency shutoff untill I obtain the correct original part. I was able to get most of the rest of the parts from the local Napa in Centralia, and I got the harder to find parts, such as the #4 JIC to 1/4" male NPT adaptor, from Industrial Hydraulics in Chehalis. All in it was about $80 or maybe a little more, including the bits to repair what I broke.
If I'd just gone to Indusrial Hydraulics in the first place, it probably would have been $25 or $30 less, but this is how we live and learn. I will remember them when I need other fittings, though. Great prices and excellent selection. Plus, they can order anything I can find in most catalogues. I'll be sure to go to them when I source new steel fuel lines. The two I got were too long and I'm not happy with my horribly amateurish bending and routing.
I'll attach a couple of pictures of the finished setup with the improvised ball valve and T, but I won't include any of the steel lines. As you can guess, I'm ashamed of how that part turned out and will be redoing it as soon as possible.