There is online bass books store called
BASSBOOKS.COM
They have a good selection of sightreading books. I would get a variaty of style especially Funk reading. You can sightread Funk everything else will come easy. Sight Reading Funk Rhythms for Electric Bass by Anthoney Vitti is a good one. Also Jim Stinnett has some good book available on his website
JIM STINNETT Check out his series Reading Bass Parts Vol 1..3
If you know any horn players ask if they know of any rehearsal big bands around. Worth going to check out the charts and they will probably let you sit-in to get some real world experinece.
Good Luck.