The Gerber LST family and the Mercator Cat were my first two thoughts, and the Spydercos are probably too expensive, at $50+, although better knives. Similar in size, price, and construction to the LSTs and Bucklites, Case makes the Caliber lockbacks with black and camo handles, and the mini Blackhorn. Another good alternative is the Bob Dozier designed, Taiwanese built Kabar folders. Different sizes, colors, thumb studs or Spyderco type holes in blades.

Do you have price and size targets, or just looking at what is in that "flat, thin, inexpensive locking" market space?