Xcentz 18W USB-C PD 10,000mAh Battery Pack | $10 | Amazon | Clip the $5 coupon on the page and use the promo code URVS6QS4
Update: Bezos found out about our sneaky little deal, and removed the on-page coupon out of spite (probably.) Our code still works though and $15 is still a solid deal.
If you want a portable, future-proof battery pack, consider this Xcentz 18W USB-C PD 10,000mAh unit. To be clear, this is designed for smaller devices, like smartphones (charges an iPhone at the maximum possible speed) but it should work on iPads and the Nintendo Switch as well. Better still, you get a USB-C to USB-C and a USB-C to USB-A cable in the box, which is amazing.
Make sure to clip the coupon on the page and use the promo code URVS6QS4 to get the best price.