Reddit mentions of Skechers Performance Women's Go Walk Slip-On Walking Shoe

Your safest bet is leather, full coverage, no holes. This is what is appropriate in a lab and required by a lot of hospitals; whether or not they enforce that, is entirely a different story. Everyone at the lab I'm currently doing rotations in wears sneakers.

I picked these up (the white ones are leather) at a Skechers outlet, because I hate the otherwise entirely unfeminine shoes that are typically offered for lab people. They're extremely comfortable and pretty cute with scrubs.

These may not be the cutest shoes to pair with your outfits, but the Skeckers go-walks are SO comfortable. I was in Singapore and Malaysia for three weeks over winter term and I was the only one in my group that never once complained about their feet. :) They are very lightweight and have great arch support.