You could get it from Iconic. But then you'd be replacing it with the exact part that broke. I'd only do that if I couldn't find anything else.
I would call a couple of companies that specialize in this sort of thing, and see if you can get some upgraded axles. I use axles from The Drive Shaft Shop on my race car, and in my FFR. Haven't broken one yet.
https://www.driveshaftshop.com/impor...ar-c-v-upgrade
I would guess - but don't know - that the BDR axle shafts are shorter than stock BMW E36 parts. I wouldn't expect to be able to simply bolt in the stock parts. It wouldn't surprise me to find out that DSS is familiar with this, and has the info to make what you need.