EC-
Forgive me for jumping in before you reply on this one...
Matthew-
I've got to run to a rehearsal, so I don't have time to check each site, but here are a couple of sites to try:
www.chaumiereonline.com/Web/ PageResultatRecherche.aspx?type=0&int=75905
Welcome to JoesDirectory.co.uk 
Classical-John-Wallace-Fantasy-Trumpet.html
Or try asking John himself. I don't have his email, but EC probably does.