Unfortunately, we currently do not sell the trackpad assembly by itself. The upper case replacement does, however, include a new trackpad assembly, as well as all of the other components in the upper case.
If you choose to purchase a new upper case, we have the free installation guide for your device right here.
Hope this helps. Good luck!
Replacement upper case assembly compatible with all Early 2011, Late 2011, and Mid 2012 15" Unibody MacBook Pros. Includes backlit keyboard, trackpad assembly, and battery level indicator assembly. — 11 available at 299.95 each.