I don't know about the band accompaniment, but the orchestral parts are apparently only available from a small company in France. It is very difficult to rent the parts and they're prohibitively expensive. If I were you, I'd look into getting the band parts. Or, if you're not married to the Cosma, choose another piece.
The Cosma is, in my opinion, worth the money for the piano reduction if you can really learn to play the piece. If not then it will only be a nice piece to own and look at!
I did the piece with wind ensemble back in december and can say that the publishers were a nightmare to deal with.(larghetto Music) They never responded to phone calls or e-mails.
It is rental only(for the wind ensemble or orchestra), and ended up costing Penn State (after it was all said and done) close to $1,000! Not to mention the 10 page contract that has to be signed, basically saying a bunch of crap, like you must include 2 free tickets for the composer to attend the concert of his work being performed. Like he is going to come to PA from France to hear his work played for the 100th time! I doubt it.