Have you tried a strap wrench? I've heard of some people having success with them, just an idea if you hadn't already tried it.
The other option would be to destroy the look of your smooth one and get it off with some channel locks, and then replace it with a standard barrel nut.
The wheeler nut wrench I got from opticsplanet came with the standard cogged wrench and a smooth barrel nut wrench as well. Probably just as well order one of those and save yourself the time of hunting for something that not many people give up. I'd be tempted to sale you mine, but as soon as I did, I'd need it or at least that's how it seems to work for me. Just FYI