Have you tried www.dexteraxle.com
They have a on-line store, don't know if they ship outside the US.
Certainly worth checking
They have a great site - lots of documentation, manuals, parts, etc.
They only show one round magnet and it did not look like yours.
Have you checked with www.inlandrv.com
- they specialize in older AS trailers - shoot them a email. Again - don't know about the shipping, but I would speculate that they do ship anywhere.
(their website only lists a tiny fraction of what they have / can get)