That seems to be the most likely scenario.
Yes, the FSU is has been having a big yard sale for a long time.
But relieving gullible Bronze-age primitives of their money does not require anything High-Tech to sell. A briefcase full of the proceeds of a Radio-Shack dumpster and a surplus cesium source to make it "Hot" would be enough to convince these morons.
As I recall, the Atomic Cannon warhead was 166 mm diameter, but its length, weight, and required fuzing modifications would put it out of the suitcase range.