Amazon.com has BlenderBottle Classic Loop Top Shaker Bottle, Clear/RED, 28-Ounce Loop Top for $3.05 as an Add-On item.
Clip the $1.75 extra savings coupon at the page, and price will be reflected during checkout.
Add-on Items are eligible for Free Shipping in qualifying orders, and Prime Shipping for Prime Members.
Note: Other Colors also qualify for this coupon, but there are slight variations in pricing.
Lowest Price after coupon applied according to CCC.