20mW 405nm Mid-open Violet Purple Blue Beam Laser Pointer Pen ,$9

Specifications:

Max Output: 20mW
Wave Length: 405nm
Output Wave: Continuous wave
Power: 2 x AAA Batteries
Size: 157 x 15mm / 6.2 x 0.6in (L x Dia.)
High quality and easy to use
Switch is convenient to use for a long presentation
This awesome 405nm violet purple laser pen will beyond your imagining.

http://www.dinodirect.com/purple-blue-laser-pointer-pen-20mw-405nm.html