Not sure exactly what bearing those trials hubs have, but I'd be doing my usual thing of using a standard 138mm hollow road axle tapped M6 plus chain tugs to handle chain tension. At best, you'd need some locknuts and spacers from the parts bin, at worst some bearing retainers similar to this:
Not sure exactly what bearing those trials hubs have, but I'd be doing my usual thing of using a standard 138mm hollow road axle tapped M6 plus chain tugs to handle chain tension. At best, you'd need some locknuts and spacers from the parts bin, at worst some bearing retainers similar to this: