Hello,
I don't believe there's really any Swallowtail/regular coat items around. I'd imagine they'd be pretty hard to create, though. It's a big item.
Perhaps you should go to "Request a Preset." Preset-makers there are very helpful, and one might gladly make you a preset with a coat on it.
Or "Request a Marking," where you could request a coat marking. That'd be helpful, too.
The solution I'd normally go with, especially in this case, is actually a makeshift marking, until I got ref sheets and someone who's ready and willing to make a preset/marking.
But, then again, I'm really lazy when it comes to this kind of stuff. Hopefully my post will encourage other item-makers to post here, and perhaps give your item request a shot. It's a possibility.