The primary sources are nil since no cast album was made and I have never seen the sheet music published.
Who owns the performing rights? Samuel French or Dramatists Play? They might know.
Take a look at who originated the roles. That will give you an idea. Swoosie Kurtz was one of them. Bette, I think.
If all else fails write to Durang care of the Dramatist's Guild which I think is still at 234 W 44th St, NYC 10036
This is a fun show. Juilliard does it every 5 years or so as one of their 4th year productions.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher