Woot offers HotHands Lap Warmer, 7-Pack for $19.99 (orig. $61.65). Free shipping for Prime Members. 

Product Description:
Experience ultimate warmth and comfort with the HotHands Lap Warmer, our largest warmer designed to pair perfectly with any blanket. Ready to use and easily portable, this lap warmer is ideal for staying cozy anywhere you go. Each warmer provides up to 8 hours of heat, making it perfect for outdoor events, cold weather activities, or home use. This case includes 7 individually packaged pouches, each containing one lap warmer.