Auto Parts: Parts number, turn signal switch, gm part number

Question
I have a 2003 Impala.  It's in pieces at the mechanic's shop now, as it had some severe electrical problems.  He tells me that I need a multifunction switch, and he also called it the turn signal switch.

What is the original part number for this switch?

He also tells me that he will only use the ACDelco replacement part, even though I found a Standard Motor Products switch that he says is the correct one.  I need the original part number to verify which switch is the correct one.

Answer
    You are stuck with going to the dealer for this switch if he won't use Standard (which I sold for years without any problems).  I really get tired of prima donna mechanics who won't use aftermarket parts, although I do understand why they do it.  The other place to get the part number is off the old part.  The GM part number is molded right into the part.