RAVPower 15000mAh USB-C PD 18W + USB-A QC 3.0 Power Bank $15 at Amazon
Amazon with ALC Direct has the RAVPower RP-PB203-US 15,000mAh USB Type-C Power Delivery (PD) 18W + USB Type-A Quick Charge (QC) 3.0 Slim Power Bank Portable Charger for $30 - 50% off coupon (check "Apply Coupon") =
$15 with free shipping on $25+ or with Prime.
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