You might want to give Tropic Aero a call and see if they still work on STS Lorans. Here is web page that looks a bit out of date:
http://www.aerosearch.com/companies/tropic/sts.html A more recent site shows only GPS equipment (
www.tropicaero.com ). I would call or email and see if they can be of any help. It seems that they would have at least a more recent database available, or can tell you who is supporting the equipment.