Amazon has the 5300mAh Anker Astro portable battery pack w/ built-in flashlight for $29.99 with free Prime Shipping. It drops to just $23.99 using promo code B2RMUW3U at checkout. That’s $26 off the regular listing, and lowest price we can find by $6. 5300mAh is about 2-3 smartphone charges or 1 tablet recharge.
Need a little bit more power? Step up to the RAVPower Element 10400mAh External Battery Pack with double the ports, and double the battery for twice the charging capability. Normally $100 but sale priced at $32.99 and Code 4VTCP6QA knocks it down to $25.99 shipped with Prime.