Not sure about the trailers.
MINI Do More makes a small one with 1000lb capacity for $825 (
HERE)
Other than that, I don't know. I seem to recall that the max towing capacity of the MCS is either 1100 or1500 lbs. Oh, and max tongue weight is usually around 75 lbs.
I eventually want to get a lightweight teardrop like the
Rascal from goLittleGuy.com