looking for a vintage bell believe it or not!
In that case, Bicloune isn't a bad bet. The blvd Beaumarchais shop is about half way between République and Bastille. The other branch (rue Froment) is close by, just across the canal St Martin.
There are also a few shops around that deal in second hand town bikes for the student/boho market that might well have a few old bells knocking about. Gepetto&Vélos of the bottom end of rue Mouffetard in the 5e is one:http://www.gepetto-velos.com/
Say hi to Annemarie from me if you drop in.
You might also give 18 Vélo Vintage a try:http://www.velo-vintage.com/
They're on rue du Ruisseau in the 18e, up behind Montmartre.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.