Have you seen the Sotto Voce mute (available from
www.hickmanmusiceditions.com) - to quote from the website
Designed by David Hickman and Eric Baker, the new Sotto Voce straight mute is perfect for soft passages such as Enesco's LEGEND, Copland's QUIET CITY, Shostakovich's PIANO CONCERTO NO. 1, SYMPHONY NO. 1, Debussy's FETES, and hundreds of other works.
I have had one of these since they came out - I have only used it a couple of times, but when you are looking for that sort of mute, you want one.
Was doing Chichester Psalms a few weeks ago and the 1st trumpet borrowed it for the ending - he then ordered one himself.