Dear Bernt,  In regard to your inquiry about the substance securing the
reeds.  You are partially correct.  The fixative is basically beeswax
mixed with rosin (and perhaps some other secret ingredient).  You may
be able to procure some commercially on-line from any company that
supplies to accordion manufacturers or musical instrument repair shops.
You might just try eBay auction:

http://cgi.ebay.com/High-Quality-Beeswax-Accordion-Accordian-/170427743081?pt=LH_DefaultDomain_0&hash=item27ae48fb69 

A number of years ago I managed to repair a small button accordion for
a friend of a friend, by just re-melting the fixative around the loose
reed slips.  Now go to it!  :)

Sincerely,
D.F. Rowe
Bronx, New York, USA