On negotiation in general, ff you have a partner or group to practice with, or as a regular small team exercise, I highly recommend Harvard's materials from their Program on Negotiation.
The material is inexpensive and can be previewed / downloaded, in full, for free (the instructor pack).
Dedicate more time to the de-briefing than the exercise, as that is where the learnings are.
Click through to one of the topics/exercises that you find interesting. An exercise can be added to your basket/cart (registration is necessary at this point, but no fee is involved for registering).
The material is inexpensive and can be previewed / downloaded, in full, for free (the instructor pack).
Dedicate more time to the de-briefing than the exercise, as that is where the learnings are.
http://www.pon.harvard.edu/store/