The reason there are few vertical bar spinners is that a short bar is basically a solid disk with a bit clipped off the sides and it is less weight efficient than a disk with spokes. Its not until you get to around 350 or 400mm diameter that spinning bars make sense. At that diameter you have to go to crazy lengths to make a vertical bar spinner work. You can still do a ~250mm bar but it won't have as much KE as other shapes with the same weight. There some ways to improve that, like an aluminium bar with tool steel tips, or fancy CNC shapes but they will add cost & complexity.

Most builders end up going with the cheapest, most KE efficient design that fits into their weight and space restrictions. In your case the ~250 diameter is between the comfort zones of drums & beaters and not quite large enough for a spoked disk. If I had to build a vertical weapon that diameter, I would go with a Hardox disk 25mm thick, with thin spokes and the smallest possible hub to keep most of the weight out at the rim.