Does anyone know where I can find mini hamburger buns in San Francisco or the peninsula?

Whole Foods has them too - including good healthy whole wheat ones. They're not technically "hamburger buns", but the right size to work just fine. I use them to make little mini veggie or chicken salad sandwiches for picnics. They also have mini-bagels that would probably work.

I saw mini hamburger buns at Cala, it's on California and Hyde. Otherwise, get really thick hot dog buns, like the ones they sell at Whole Foods, and cut them into thirds. They make good slider burger buns. ;)

Try the Smart and Final grocery chain. They also do restaurant supply.

at the grocery store

molly stones has them