Toys"R"Us offers the Nerf Super Soaker FlashFlood Blaster for $3.88. Choose in-store pickup to dodge the $5.99 shipping fee. That's $15 under the lowest shipped price we could find elsewhere, outside of the mention below. It features two nozzles, holds up to 23-fl. oz., and sprays up to 38 feet.
A close price: Amazon charges $3.88 with free shipping for Prime members, albeit only with orders of $25 or more.
Update: Specs corrected