Help! First unknown broken part! Options

[desmomini]

In a desire to protect the hellhole, I decided it prudent to replace the 9 year old Interstate battery with a new sealed Optima 34R. In the process of undoing the battery cable, I broke one of the battery terminal bolts. No big deal, right? Well...this one had a box end with a hole in it, accepting a smaller bolt that screws down two pig tail wires.

I don't understand exactly why it was wired this way, but it was, somewhere in the past, plus there's a battery cutoff switch. In any case, I can't start the car unless these two pigtails are also connected to positive, and they are just a hair too small to fit on a standard battery terminal bolt under the nut (they just won't thread on the bolt, which is too big for them.)

You'd think a part like would be simple to find, as it seems like car audio installers, etc, would regularly use something like this, but I can't find anything like it anywhere! The closest I've found are replacement terminal ends, and I'd like to not the battery cable if I don't absolutely have to.

This seems like such a clever little piece of hardware...where can I find one?