Basics - now Nomatic - slim minimalist wallet for $6 each after coupon code "HAPPY". Shipping is $4 regardless of how many you order. Available in multiple colors.
Was front pages 2x this year at $13 so should be a good deal at $10 (or less if buying multiple). Currently rated 4.6 out of 5 stars on Amazon with almost 1,100 reviews and selling for $20.