At the same trip to get the spoke wrench I swung by a person who was selling an used swing. I'm doing a hardtail so I don't really need the whole softail swingarm, but it's a way to get the axle plates.
This is the swing it self
This is the swing it self
and the axle plates are these parts of it.
This is pretty much the cheapest and most convenient way to get the axle plates. One option is to just make a custom plate out of piece of steel which ensures the freedom to go after certain looks. But it's pretty much work and needs some real tools. The other option is to order custom stuff, which is the most expensive approach. And the third option would be to buy the plates just as is, but buying them new costs more than whole used swing.
The idea of the part is that the rear wheel axle goes through there and the axel plates connect the frame tubes here. If you are wondering what is the whole point of the swing it would be originally the tail part of the frame, little like this. But you can also see from the picture what else needs to be done. The upper part of the frame should form pretty much a straight line from steering axle to the rear axle, which I very skill fully illustrated there with Gimp.