[Kevan]

Make your own axle tube, get a length of 1/8" brass tube the right length to fit inside both bushings (put the recesses on the inside), when you've got it the right length take the bearings and brass tube out, slide them onto an old axle smeared in oil, put axle collars up to the bearings or slide a length of silicone tubing over each end to push it all together then solder the brass tube into each bearing. Smearing the axle in oil will prevent solder sticking to it.