Crocs via eBay offers its Crocs Men's or Women's Duet Wave Flip Flops
in Nautical Navy/Concrete (pictured), Black/Charcoal, or Espresso/Khaki for $19.99
with free shipping
. That's $3 under our mention from a month ago and, outside of the mention below, the lowest total price we could find by $8. They're available in men's sizes 4 to 13 and women's sizes 6 to 12, although not in all size/color combinations.
A close price: Amazon
has them in four colors for $20.99 with free shipping via Prime.