Target offers the Contigo SnapSeal Byron 20-oz. Stainless Steel Travel Mug in Grey for $9.39. (Pink is available for cents more.) Choose in-store pickup to dodge the $4 shipping fee. Outside of the sellers below, that's the lowest price we could find by $3, although we saw it for a buck less two days ago. It purportedly keeps drinks warm for up to seven hours and cold for up to 18 hours.
Of note, Walmart has it in Vivacious for $9.49 via in-store pickup, and Amazon charges about the same when you spend $25 or more, with free shipping for Prime members.