Try:
BAE SYSTEMS, Asset Management, Trading and Services
Tel: +44 (0) 1707 271777
Fax: +44 (0) 1707 255555
They manage the OEM's for portfolio of Jetstreams and other types - over 400 aircraft in all. According to the corporate blurb this is the 3rd largest leased fleet in the world , making them the worlds largest regional aircraft lessor.
The guy I last dealt with left a year or so ago. Just don't ask for Del boy!
Or try the Virginia office:
Tel: +1 703 736 1080
Fax: +1 703 736 4209