Tony et al:
Al-Ko Kober (maker of the axles on Cobra trailers) sells custom
axles in the USA. Both electric and hydraulic brake systems are
available. The one I ordered from Axle, Inc a while ago was an easy
fit. Here's a link to their form, to measure the custom axle.
http://axleinc.com/_wsn/page10.html
You could also check with Williams Soaring to see if a European axle
(they stock them) would fit your trailer, which uses mechanical brake
actuation. You could send them the completed form.
Bewa The parts room at Williams can be addictive!
Williams: 1-530-473-5600
Jim