After getting burned by AST in a previous life, not surprised they don't have a US distributor any more.
Maybe talk to Vorshlag and see if they can set you up with a bilstein insert in a old housing, I guess Stuart can then service that moving forward.
I just started using a Camaro kit that is derived from the bilstein take-a-part shock kit, non adjustable, but it came way under the CMC limit. Guy is out of California and only does camaro stuff but maybe you can give him a ring:
http://www.unbalancedengineering.com/Camaro/Bilstein/
Camaro@UnbalancedEngineering.com