I have about a month and a half to work up a solo. I wish it could be longer but unfortunately, that's all the time I'll have.

It needs to be a movement from a standard concerto, sonata, or equivalent. I don't want something extremely long. A lot of the solos I'm seeing seem to be quite lengthy like the Mozart Concerto (48 pages). I'm assuming part of that is the piano part but it still seems very long. Are there any really good clarinet solos that aren't extremely long and that will demonstrate good technique and tone, etc? (played well of course)

I'm really worried about not having a lot of time but I've got to find a good piece that I'll be able to work up in time and play really well.

I'm first chair in my band and have been in the All-State band the last two years so maybe that will give an idea of the music I could play.

Any suggestions would be greatly appreciated!

Take a look at the Mozart. Really.
Also, I'm playing Weber's 2nd Concerto and Premiere Rhapsody by Debussy. Another easier option would be the 4th movement of the Saint Seans Sonata.

You should play a movement from the Poulenc sonata. Take the first movement. When I auditioned for college(the norwegian academy of music) I played that one. It has lots of dynamics, slow parts and tecnically parts. Everybody I competed against also played it in addition to the pieces you have to play, witch in Norway is Weber-Consertino and one of the movements in Schumanns fantasy.

I agree with the Poulenc. You could even do the whole thing, its only about 13 minutes give or take. I also suggest Rossini/Weber's Introduction, Theme and Variations (without repeats of course)