Repair or replace Kohler shower handle/valve?
I just moved into a 9 year old house and the shower in the master bath has a slow leak (drips at the shower head, not handle). It's a single handle (turn) style shower handle/valve by Kohler. I've taken it apart and replaced the rubber O-rings which looked a bit worn. I neglected to note the model #'s of the parts. It has a large brass valve-body and a plastic cased valve/cartridge which is where I suspect the slow leak is. It is a shower-only model, no bath.
With a fixture that is 9 years old, is it possible to find replacement valve cartridges? If not, do I have any other options besides having a plumber tear into the wall to replace the entire valve body along with a new handle?
This may seem like a stupid question, but I work in Pediatrics and not home repairs. ;) Any help/advice would be appreciated.