Have you actually asked them? Just because they don’t sell after market doesn’t mean they won’t repair, in their interest to have one of their rims after all!
They seem pretty clear about it, they only build/repair them themselves which involves send them to the USA:
http://www.amclassic.com/en/faq.php
Why doesn’t American Classic sell individual rims?
We are often asked this question. Our rims are lightweight and can be difficult to build. We handle all wheel rebuilds in-house because our experienced wheel builders maintain our quality standards. Sorry, we do not make exceptions to this rule.
I crashed my wheel and damaged my rim. Does American Classic offer a Wheel Rebuild Program?
American Classic offers service provided by our highly qualified Technical Staff and Wheel Builders. Services include wheel rebuilds, hub maintenance, hub cassette body and bearing changes, and general repairs. 90 day guarantee on all work. Call our sales department for price estimates on parts and service work. Our sales team will take your order and issue a return authorization (RA) number. American Classic does not sell individual rims.
Crests seem the sensible option tbh.