Looks like he's already onto it Andy!

Yes, that rear axle is a sweet bit! Not sure how it compares price wise to the HRC piece. I checked 2-stokes and couldn't find anything. I have a machinist friend who has made a few before from a stock axle. He bores the center, presses then welds a new stub shaft for the wheel side, threads it and fabs a nut to match. Not a bad solution. He runs one on his RC45 (street) so I would imagine it would be up to the task on a RS250 racer.
_________________
Andre E. Benguerel
1996 Honda NSR250R
Daijiro Kato/Fortuna Replica #74

2000 Honda RS250R (NX5)
2008 Honda RS250R (NXA)
AFM Expert #430