I'm not a contracting guy but will share what I know.
Many knives have NSN's (national stock numbers) assigned to them (I know the Benchmade autos do, ordered some). This lets a unit order them through their standard supply system. Since they must keep some in stock then I guess those guys would have a contract, not sure about that part though.
If I remember right though almost anyone can submit something to be given an NSN. Just in case someone wants to order it and to keep gov't business open to smaller guys.
The situation gets a bit more cloudy though since a unit can do a local purchase for almost anything the CO will sign off on. Therefore, if the boss was a big Cold Steel fan then he could buy Cold Steel stuff for his guys. If a company wants to get some ad mileage then they could easily donate or sell at a cut price to a unit.
My opinion is that many people really blow the military contract thing WAY out of proportion. Someone has a contract to sell us everything from tampons to floor wax, they aren't using it as an advertising ploy.