We have pieces in the following keys for Clarinet Duet:
1-20 of 59 Clarinet Duet Pieces in Bb major

Trad.
Good King Wenceslas

Haydn
Three Duets - Menuetto 1

Mozart
Twelve Duets k.487 no.10

Mozart
Twelve Duets K.V. 487 no.9

Mozart
Duet from 'Seraglio'

Mozart
Twelve Duets K.V. 487 no.8

Bach
Duet for Two Clarinets, Wq.142 (H.636)

Trad.
We Wish you a Merry Christmas

Franck
Panis Angelicus

Tchaikovsky
Theme from Symphony No.6 2nd Mvt

Elgar
Symphony No. 1 Opening Theme

Trad.
Blow the Wind Southerly

Trad.
Au claire de la lune

Trad.
Ding Dong Merrily on High

George Cohan
Over There

Tchaikovsky
March from The Nutcracker

Beethoven
Allegro and Minuet - Duet, WoO 26

Beethoven
Allegro for a Musical Clock

Bach
Concerto for Two Violins BWV 1043 (Slow Move...

Bach
Sheep May Safely Graze from Cantata 208