Mk3 one piece axle?

Hi, I'm considering making a one piece axle for the rear wheel of my bike which has a stock Mk3 swing arm & disc wheel mounted .
I just do not like the way the stock set up is designed with the dummy axle bored out to accept the male axle.It looks like a bad design waiting to fail,yet I have not heard of any failures.
Has any one found a generic one piece axle from another bike that will replace the Mk3 axle with out too much modification?
I think I would perfer one to fit the existing spacers rather than enlarge the swing arm slots & speedo drive.
Does any body sell one all ready made?
Thank You
Bruce Macgregor

Mines a 70 model and I'm not using the speedometer drive. Old style, 2 bearings, no cush drive. My bearing spacer had a 15mm ID with a crazy little shouldered spacer to fit in the 17 mm ID bearings. I didn't look for 15mm axles, there may be some out there. 17mm are pretty common. I ended getting one off a CB400 Honda for cheap on ebay.

I had one made for my Mark III monoshocker from Caterpillar heavy equipment inventory. I had to have it shortened and re-threaded. Mine remained single-diameter due to the fact that i used chain adjuster blocks inside the box-section swingarm; you could have yours shortened, shouldered and re-threaded to suit your needs.