Contigo Shake & Go Fit 28 oz. Mixer Bottle - $8.00

Walamart has the Contigo shake & go mixer on rollback for $8. There's no stock online but plenty in stores around me. It rings up as $13 but if you show the cashier the website they'll adjust the price. The same bottle sells for $17.99 on amazon (not to be confused with the "shaker" version that's cheaper and doesn't have the screw on seal). It's a pretty solid protein shaker, BPA free, rounded bottom, easy to clean, leak proof seal, and made with thicker walls than most bottles.