Re: Bob in St. Louis
Gundigest.com has exploded diagrams for many Astra models, but I didn't see the 900 listed. You might contact then anyway and see if they know anyone.
Have you tried any sites like gunboards, or surplusrifle? They're sites for milsurp collectors.
The only I found was a disassembly guide
The best things in life, are not things.