Generic NeoPixel Digital RGB LED Weatherproof Strip 30 LED -1m - (WHITE) (JS-1204) (3D4)

This is the most affordable (by meter) NeoPixel strip.  By the pixel, the 144 LEDs/ meter is cheaper, but if you're more interested in length than # of lights, this is the way to go. Also, if you are cutting these apart, the spacing of the 30/meter has a good size border on each one.

Comparable items:

NeoPixel strip 144 LEDs/meter: Less expensive per LED, but more expensive overall (because there are more LEDs).

Loc: 3D-4