Walmart discounts a selection of pools and water toys, with prices starting at $9.88. Shipping starts at $4.97, but in-store pickup is also available. (Many orders of $50 or more are also eligible for free shipping.) A couple of best bets, both with free shipping:
Home Depot offers the Step2 Neat & Tidy Cottage II Playhouse, model no. 841600, for $129.99. Opt for ship-to-store pickup to dodge the $55 shipping fee. That's the lowest price we could find by $20. It measures 46-1/2" x 35" x 51" and requires two AAA batteries (not included).