Quick Question - adding outlet above cabinets

I want to add an outlet above my cabinets (about 1' space from top to ceiling) for under cabinet lighting. I plan to plug on the transformer above the cabinet and run low voltage to each LED strip under each cabinet.

Since the new outlet is above the cabinets but still in the kitchen, am I supposed to pull power from my dedicated 20a kitchen outlets, or from the above sink light switch which is on a different 15a circuit?

I can do either, but would prefer the sink light switch if that's within code (make it a 2-gang box with addl. switch).