B&H Photo Video offers the HP Power Pack Plus 18,000mAh Portable Battery Pack Bag for $34.95 with free shipping. That's $15 under our October mention and the lowest price we've seen. (It's the best deal today by $75.) It charges up to three devices simultaneously via two USB Type-A ports and one USB Type-C port. It also includes a 7.4mm-to-4.5mm tip adapter and cable for charging HP laptops. (Laptop charging requires the bag be plugged in via the included power adapter.) Deal ends December 27.
With these companies, it might be easier than you think to negotiate your monthly bill down.