Talk to a local welding shop near you.
They will know the details of the swing away hinge that will be strong enough for your motorcycle. Make sure to tell them how much your MC weighs, along with the handlebar width for spacing away from the back of the vehicle, the length of the overall MC and the distance between the axles for the length of the carry rack.
What you save in shipping charges from an internet company, you may pay for the local custom solution. So, the money part may be a wash, but, you'll get exactly what you want. And, bigger than that is if you have any issues or redesign ideas your builder is local to you.