Woot offers Anker 20,000mAh 15W Powerbank 2-Port (USB-C & USB-A) for $26.99 (orig. $49.99). Free shipping for Prime Members.

Product Description:
Experience the ultimate in charging convenience with the Anker 326 Power Bank (PowerCore 20K). Boasting an impressive 20,000 mAh capacity, it powers most smartphones over 4 times and tablets at least 1.5 times. Simultaneously charge up to 2 devices, all while staying informed about the battery percentage through the intuitive digital display. Stay powered and connected effortlessly.
Product Features:

• The ultra-high capacity dual-port portable charger
• Faster and safer charging with ANKER advanced technology
• 20,000mAh is enough power to keep your phone, tablet, and other devices charged for days
• Effortlessly charge up to 2 devices concurrently, ensuring all your gadgets stay powered up without compromise
• Stay informed with the digital percentage display, offering an intuitive and precise representation of the remaining power
• Has dual USB-C and USB-A ports