In my cd collection I have Viola Concertos by:
Samuel Adler
Kalevi Aho (with chamber orchestra)
William Alwyn (Pastoral Fantasia with string orchestra)
Sir Malcolm Arnold (with chamber orchestra)
Stanley Bate
W.H. Bell('Rosa Mystica')
Sir Richard Rodney Bennett('Lady Caroline Lamb': Elegy)
Michael Berkeley
Ernest Bloch (Suite and 'Suite Hebraique')
York Bowen
Benjamin Britten ('Lachrymae' with strings)
Geoffrey Burgon ('Ghosts of the Dance')
Arthur Butterworth
Frederick Delius('Caprice and Elegy')
Cecil Forsyth
Benjamin Frankel
Steven R. Gerber
Morton Gould
Eero Hameennniemi
Howard Hanson('Summer Seascape No.2' with strings)
John Harbison
Paul Hindemith ('Der Schwanendreher' with small orchestra, 'Trauermusik' with strings, Concert Music, op. 48 with large chamber orchestra, Kammermusik
No.5 with large chamber orchestra and Kammermusik No.6 for viola d'amore)
Alun Hoddinott (Concertino with small orchestra)
Vagn Holmboe (Chamber Concerto No.5 with chamber orchestra)
Gustav Holst ('Lyric Movement' with small orchestra
Herbert Howells('Elegy' with string quartet and string orchestra)
Gordon Jacob Viola Concerto No.1, Viola Concerto No.2 with strings, Concert Piece, Three Pieces and 'Passacaglia Stereophonica')
Joseph Jongen (Suite and 'Allegro Appassionato')
Viktor Kalabis('Tristium'-Concertante Fantasy with strings)
Giya Kancheli (Liturgy-'Mourned by the Wind')
Erland von Koch
Elizabeth Maconchy ('Romanza' with small orchestra)
Bohuslav Martinu(Rhapsody-Concerto)
David Matthews(Concertino 'Winter Remembered' with strings)
John McCabe (Concerto funebre with chamber orchestra)
Darius Milhaud (Concerto No.1)
Gosta Nystroem ('Hommage a la France')
Paul Patterson
Krzystof Penderecki
Allan Pettersson
Walter Piston
Miklos Rozsa
Edmund Rubbra
Ahmed Adnan Saygun
Alfred Schnittke
Ralph Vaughan Williams (Romance and 'Flos Campi' with wordless chorus and small orchestra)
Sir William Walton
Most of these are fairly modern works and not sure obviously what your taste might be

If any of them strike you or might interest you then I am happy to make particular recommendations.
The Stanley Bate is gorgeous however
