@FJTRoy,
saw your professional balancer stand, mulled it over a while, checked my workshops stock and found:
-a 12 mm treadbar
-2 12 mm wheelnuts
-2 12 mm regular nuts
-2 bearings 10x25x8
-1 8 mm nut
-1 8 mm washer
Our LIKEs and most probably other Kymcos have an rear axle diameter of 18mm.
So, this two old wheelnuts hat to go into my lathe and where maschined in shape to fit tight with our axles diameter.
Then this wheelnuts where drilled out to 12.5 mm to slide on mentioned treadbar.
This treadbar was reduced on both sides to 10 mm, to have a seat for my bearings. One bearing was glued in place, the second one is removeable to fit this "balancing axle" trough our rim.
The "open" end of this treadbar was turned to 8mm and got a 8mm tread at this end, for a safety nut.
My both sawhorses got halfmoon shaped grooves and that was it. Both regular 12mm nuts are used to push the "wheelnut cones" in the rim.
Ready for balancing.
I tried my rear spare wheel, spins easily without rocking or any other caprices.