Jazz students are often looking for new chords for the standards they are playing. This blog offers you some suggestions if you are unable to transcribe.
1. The iReal Pro app is a useful source. It doesn't always have the most exciting chords, but it does help you move on from the fakebook.
2. YouTube transcriptions, though not always reliable, will help you explore new harmonic ideas.
3. The Real jazz Solos Book by Hal Leonard is a reliable book to consult.
You've got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.
I'm a professional pianist and music educator in West Toronto Ontario. I'm also a devoted percussionist and drum teacher.