I recently bought a restored organette similar to the Celestina (a
Symphonian, I think), but only after spending a lot of time with the
vendor trying to decide between that and a Coronet (very similar to a
Celestina; plays same 20-note rolls) that needed restoration.

The seller, who had been restoring organettes of all types for years,
said to use Zephyr Skin for the pneumatics inside.  This is a thin,
light, nearly transparent natural substitute for pouch leather.  I still
have some from 25 years ago, and it seems to be still good.  I think PPCo
still carries it.  Otherwise I'd recommend regular brown pouch leather
for those tiny pneumatics.

Since I have a sluggish bass note on my organette, I may have to put my
time (and my old zephyr skin) where my mouth is fairly soon.

BTW, zephyr skin is fussy about what types of glue it will stick well to.
White glue and plastic glue aren't reliable.  Someone recently posted
here which type is good, but I forgot already.

Mike Knudsen