LoHiDirect via Amazon offers its LoHi 4,000mAh Ultra-Slim Extended Battery Case for iPhone X in Black for $39.99. Coupon code "IP39XXOF" cuts that to $24.39. With free shipping, that's $16 off and the lowest price we could find. It features a semi-open TPU case body with microfiber liner, Lightning connector for charging or headphones, color-changing battery indicator, and on/off switch. Deal ends January 28.