C'mon, at least buy them from the Chinese for a $100 or less a piece.
The problem with that is that they'd be too cheap, and thus more difficult to believe in.
Assuming for a moment that in the hands of a competent operator these things *do* find bad stuff more often than random chance would allow, you'd want them to be well and consistently made. You would want them built by a company that didn't skimp on materials and that wouldn't make random substitutions if certain parts or materials were unavailable. You'd want them as "mil-spec" as possible, so they'd survive field service. You'd want them to come from somewhere with a little credibility in the security field, as this mob seem to have from some of the other devices and bespoke vehicles they produce or distribute - this is not the kind of thing that you could get away with buying from just anywhere, and in the absence of the ability to properly and scientifically test it you'd need to rely on the thing's pedigree to some extent.
As for the assertion in TFA that reporters managed to carry AK-47s in their car without being challenged - perhaps what's being detected isn't the physical presence of weapons or explosives, but the intent of the driver and passengers. If a driver knew they had a bomb and had a belief that the checkpoint had a magic bomb-detecting divining rod, they'd be more likely to be nervous. Perhaps these devices give the operator a little more confidence that allows them to subconsciously take more notice of other behavioural cues. If that was the case, then a driver who didn't know the vehicle was packed with explosives or a driver who was a cucumber-cool psychopath could reasonably be expected to not "trigger" the device. Similarly, someone who was nervous in the presence of people with guns and badges and roadblocks could be expected to be spotted as being "uncomfortable" by the operator - and the gold teeth and perfume false-positive stories are intended to allow the operators to continue to believe in their skills and the device. You could probably get similar results from people who were conditioned to believe they were tapping into their own psychic potential, with a couple of potential drawbacks - if they fail with a prop they can blame the prop and the potential unreliability of the process rather than themselves, and they're less likely to be killed by the oppositiion if they're not seen as some kind of magical and irreplaceable person.
Sure, it's security theatre rather than a security device per se, and in use is a cross between a confidence trick and a carnival act, but that might just get results for reasons other than its own "bomb detecting" ability.