Amazon offers Prime members the Chamberlain Universal Laser Garage Parking Assist, model no. CLULP1, for $16.98 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $6.60. Walmart has it for the same price and Home Depot has it for a few cents less, both with free in-store pickup.) That's the lowest total price we could find now by $2, excluding the mention below, although we saw it for a buck less in May. It features plug-in installation, class 2 laser, anchor, screw, two wire nuts, power adapter, and instructions.

A close price: NextWarehouse has it for $17.75 with free shipping.