Amazon offers Prime members the Nerf Super Soaker Freezefire Blaster, model no. A4838, for $6.60 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $6.29.) That's the lowest price we could find by $3. It features 23-oz. capacity and firing range up to 38 feet.
Orders placed via Prime by December 22 are guaranteed to arrive in time for Christmas. (The deadline for standard shipping is today, December 19.)