Ebay offers Refurbished EcoFlow River Pro 720Wh Power Station for $399 (reg $599) with free shipping.

Product Description:
The EcoFlow RIVER series is a compact, portable power station that is built for taking your adventure into the great outdoors. Whether you are camping, over-landing, tailgating, or boating, the RIVER series provides reliable power that lets you take your adventure anywhere.

• Support 80% of essential devices with X-Boost mode on;
• Fast AC recharge from 0% to 80% in 1 hour and fully charged in 1.6 hours with the X-Stream technology;
• Easy and user-friendly control with the EcoFlow App, visualizing the power usage in your hands;
• Modularized capacity to suit your needs, from 720Wh to 1440Wh with the Extra Battery.