Love the product that CitySlips provides to alleviate this problem. CitySlips makes ballet flats that come in a bag.
Tuck them away in a purse and swap out your uncomfortable heels for your comfy CitySlips. The CitySlips bag converts to a tote to then stash away your awesome-looking but not-so-comfy heels for the rest of the night.
Use coupon code 10OFF for 10% off your order at CitySlips.com.