I know it's very amateur and Heath Robinson and you can all chuckle, but faced with the same problem, not having a lathe big enough nor a deep enough table on my modest miller, and not wanting to be sending wheels away for ages, I made the attached to rectify the drum on the front of one BSA.
All it is is a fly-cutter bit held in a bit of round mild steel bar with a milled flat one side for locking it by means of the smaller tommy bar, mounted on a piece of thick steel bar in which the tool can slide (and be locked for and aft and side to side by the screws and the ugly 6mm rod with nuts on). The big piece of flat bar is drilled to go exactly over the wheel spindle and be done up fast with the nut that holds the backplate.
With the wheel spindle mounted in clamps in a big vice, tool locked on and held rock steady (with an extra arm attached to stop it budging under any circs), I then rotated the wheel slowly by hand while introducing the tool very gently by means of the long screw, having set the depth of cut on the sliding block to take a thou or two at a time at the narrowest points of the drum. It got rid of 35 thou of ovality in many stages and didn't leave me with a bit of corrugated iron either. I just kept running the tool down (which is spring-loaded in the bit of blue tube to get it to come back up again) at the same settings time after time. Finish not per factory obviously, but smooth to the touch, and more importantly, a round drum, concentric with the spindle, which works a million times better.
With a slight mod (collars and spacers made up to suit), it finish-cut a home-made drum liner for an AMC front end after shrink-fitting it, with another OK (to me) result. Not something to do on a perfect and beautiful machine perhaps, but on my old clunkers it's worked fine and no-one's said to me 'wot, no brakes!'.