You're going to have to make or get the brackets separate from the wheel adapters.
RC wheels use one of two standards: Either a fix-pin on a shaft, or a "hex" that goes into the hub. Neither is a standard used anywhere else, where you will have keyways, or D shafts, and/or set screws and shaft collars (and perhaps press fit for bearings.)
For a robot suspension I'm working on, I ended up making adapters from a D shaft with set screw to 14 mm hex center by milling out of aluminum and drilling/tapping holes for the set screws. I then cut the brackets out of aluminum on a mill, too.