Probably a dumb question

Not only are you looking for uncommon brands, assume the production on such may be very limited and the owners may keep the units for a very long time or never sell. 

You might want to set up a Saved Search on US Audiomart for the brands you are seeking. This will give you notification anytime something new is posted that is a match. 

https://www.audiocircle.com/index.php?topic=186144.0

@speedthrills  They are not inexpensive and the mark-up looks high. However, the OP is looking for hard to find items and SkyFi are hungry at tracking down desirable gear. 

@noromance Skyfi's prices are ridiculous imo...

Check out The Audio Circle marketplace.  You might get lucky.