Ebay offers Open-Box WaterPik Revive Cordless Portable Water Flosser for $19.89 (reg $49.99) with free shipping.

Product Description:
Battery-operated, portable, and waterproof design makes the Cordless Revive perfect for small spaces, travel, and use in the shower. Enjoy an incredibly fresh, clean feeling and better oral health.
This model comes with 3 tips including our Orthodontic Tip designed for cleaning braces and orthodontics. It features 2 pressure settings, 3 AA batteries, 30 seconds of flossing time, and a lightweight and portable design.
Waterpik is the #1 recommended water flosser brand, clinically proven and accepted by the American Dental Association (ADA) for safety and effectiveness.

• Overall Length: 11.75 Inches
• Suggested Age: 12 Years and Up
• Includes: Instruction Manual, Flosser, High-Pressure Tip, Orthodontic Tip
• Material: Plastic
• Features: Cordless
• Power Source: Battery
• Battery: 3 AA Alkaline, Required, Included