JIJ US via Amazon has for 2-Pack JIJ Rechargeable Electric Hand Warmers (Black) on sale for $9.99 when you apply promo code SOPFNHUZ at checkout. Shipping is free w/ Prime or on $35+ orders.

Thanks to Deal Hunter Navy-Wife for posting this deal.

Note: Promo codes are typically for one-time use and don't always apply seamlessly. If you run into this issue, refresh the page, re-enter the code, or revisit the cart page.