I would also check
www.bikeman.com - who has a lot of older parts.
The brake levers should be easy - even to replace with new parts - but
the thumb shifters might be tricky. New components aren't compatible
with the old 6 and 7 speed stuff. (You could replace the entire
drivetrain, but that would cost more than the bike is worth).
You might check with a few bike shops in your area that have been in
business since the 80's. Most shops have a box in back that all the
"old but works" stuff gets stored.... if you remove one of the shifters
and say "got any of these" you might get lucky. (Half the time they
won't charge you for anything from the box).
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