Looks like the modern way to do this is with LGB part #67403. The cost per axle seems to be about the same as the cost of brushes and wheels separately also.
LGB quetsion... I have some passenger trucks like LGB #67380.
Note the tubular section on the arm between the coupler and the pivot.
I'm pretty sure this is for electrical pick-up brushes like those that come with LGB #63193. Is the intent that people would use LGB #63120 brushes with the 4-axle trucks?