Woot offers 16-Pack Solar Waterproof LED Deck Lights for $19.99 (orig. $28.99) + free shipping with Prime.

Product Description:

The Solar-Powered Waterproof LED Deck Light, manufactured by HAKOL, is shaped at an angle and perfect for illuminating your fences, railings, steps, flower beds, and more. The Deck Light is waterproof, weatherproof, and heat-resistant. Solar power will save energy and prevents the need to turn the lights on manually.
Features:

• Solar-powered
• Automatically turns on when it gets dark
• Waterproof and moisture-proof
• Energy-saving
• Shaped to illuminate steps, railings, or fences
• Color is Warm White
• Dimensions: 3.46 in. x 1.77 in. x 1.84 in.