By far the best solution is to try and find a replacement reed.
I have quite a selection of brass reeds but (a) I'm in the UK,
and (b) I haven't seen Melodia reeds, so I couldn't be sure of
a replacement without some additional information.

Greg, if you want me to try and find a replacement, e-mail me
with the following information if you can :-

1 - The shape of the reed base (some are just oblong, some are
round at one end).

2 - Dimensions of reed base - length, width and thickness
(and if it tapers, by how much).

3 - Dimensions of the reed tongue (or at least the hole in
the reed base) - length, width and taper if any.

4 - If possible, the notes played by the adjacent reeds as given
by a tuning meter set to A=440.  I would need the note indicated
on the meter and the degree of sharp or flat in cents.  If you
don't have a meter, see if you can find a musician how can help
with this bit.

On this basis I can search for a suitable reed, or possibly
re-tune one.

The reason for #4 above is that the tuning standards of most
organettes is quite variable, so just finding a reed marked C#
won't necessarily give the right note.  The size of the base is,
of course, critical for fitting the reed, and the size of the reed
tongue will determine its general volume and timbre which needs
to match the rest of the instrument.

Replacing the tongue is possible with the right thickness of sheet
brass, cut and filed to size and riveted in place, then tuned, but it
is "fiddly" and time consuming.  If you want to try this yourself,
e-mail for more advice.  It's probably best to e-mail me direct on the
below address (removing the ".geentroep") if you want to go ahead.

John Farmer, UK
john@musicanic.com.geentroep
http://www.musicanic.com/