My $0.02
Zhodani culture prizes law & order. Their use of psionics has eliminated dishonesty, unhappiness, and aggression from their society. It's a very boring society as a result and because all of the Proles are happy, it's a very creepy one too.

District 268, being lawless, is not like that at all. The Zhodani who would venture there would have to be very brave and very industrious traders as a result.

Naturally, it's a great place to plant spies; and advisors who shelter and train Ine Givar rebels.
My take: "oh look, it's another Imperium that wants to dominate us. Let's do some trade witht hem but other than that, )(*#$ those guys."
It's a supply and demand issue. The helmets will be available in places where Zhos are more common. It's not Imperial proprietary technology and the few worlds in the District that have a high enough TL will have the capacity to make them. And don't forget the Sword Worlds are nearby too.

ADVENTURE SEED #1: A Zhodani noble has set up shop, a small import-export business, on a D268 world. It's a cover for a psionics institute. His real purpose is to use telepathy to infiltrate the planet's society with psionicists who will work their way into the local government and ultimately give the world over to the Consulate.

ADVENTURE SEED #2: A disgraced Zhodani war veteran has gone to one of the more primitive worlds in D268 to "retire." He has begun to use his psionics to brainwash local tribesmen to form a cult of personality around him; or even a religion with him as a godhead. Communications from the Consulate to him have been responded to with bizarre, cryptic answers that indicate he is insane.

The PCs need a mission. And for their sins, they have been given one. Terminate, with extreme prejudice.

"The horror... the horror..."