I've no experience with the B4 so take this with a pinch of salt, but you should be able to add a hex to the pin drive on the axle to allow you to run 12mm hex wheels.
At this stage 12mm hex is more-or-less industry standard across 2wd and 4wd buggies, so there is no shortage of them available. I quite like the JConcepts wheels as you get two pair ~£8 where RRP on TLR wheels for example are £8 for a single pair.
One thing you do need to look out for is the depth of the wheel, some manufactures have a large shoulder or un-threaded part on the driveshaft which requires a much thicker wheel offset to fill so that the nut can tighten up against the face of the wheel rather than running out of threads.
If the b64 is anything similar to your buggy, its possible to run tlr 22 rims on both front and rear as the threaded section on the axles goes almost all the way to the face of the hex and thus its not a problem.
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