Single side mount wheels have been around for a while. Cannondale dabbled with them some time back.
As you suspect, they often require a special hub and axle which is more like a pedal spindle than typical hub. However, some have standard shells and axles that are simply moved across for single side mount.
You might find one if you search for wheelchair or sulky hubs, as these are typically of this design.
Before jumping in, keep in mind that they need a special fork designed to handle the twisting force that the system creates.
Last edited by FBinNY; 04-03-24 at 12:36 PM.