I've been researching something quite different this morning but by chance came across these web references :
http://www.timesaversforteachers.com/index_page0015.htm gives a sample teacher-student contract, while
http://eqi.org/tscont.htm gives a critique of another.
I don't think the next two are exactly the same type of contract that you're thinking about, but they might be interesting in terms of how to establish contracts in general. The first is about
behaviour contracts with younger learners ,and this also has further links. I also wrote a short article about how I once used a learning contract usefully
here.
But Carl Rogers remains the guru. I would recommend his book to anyone who ever wants to set foot in a classroom by the way.