About 5 years ago, I was part of some research in testing external SHB traps. The lures were baited with a dough-like ball. It did attract SHB as well as other beetles also. I have not been aware of anything on the market from the study, and that is why I asked about it.
The external trap seemed plausible at the time, but I think recent research indicating the SHB's main attraction is to hives under stress. Seems robbing, opening up a hive, predators, and anything else that will cause the bees to send out alarm pheromones, is irresistible to the SHB. They will fly miles to a hive under stress or alarm. I guess a trap with these same pheromones would work. Maybe that has been the reason of nothing to date. They started on one thing and stopped in favor of another more effective approach.
It would seem to me that all you might need to do is attach fatbeeman's hive beetle trap to the underside of a hive (I would guess as close to the front entry as possible). I have not used fatbeeman's trap myself (yet) but my somewhat famous neighbors to the south gave his trap a go this spring and have reported to me they were somewhat effective.
fatbeeman had a short video on constructing the 'trap'.
I saw his video and that's actually what made me think of it because I was thinking that I wouldn't want a beetle crawling in the boric acid then crawling through the rest of the hive before dieing... so I was thinking that if the trap was outside the hive that might be prevented. But then that got me thinking about the sandwich container trap, since it uses an attractant that maybe it could lure them away from hives or intercept beetles headed toward the hives before they got there. So that's how I got around to this question.
Even if they aren't as effective outside the hive, I think I've seen a few articles saying that a sandwich container trap costs less than 50 cents to make, and fatbeeman's trap looked like it was even cheaper, so they're cheap enough that if they work at all, no matter how ineffectively, it might be worth it to put a few out there to nab these suckers before they get to our girls.