My gut reaction is that a hardware implant would be too costly so there's no way they'd actually do that but I guess when you can steal $92M, anything is possible. They could even fab an esoteric chip and still make a profit.
PCBWay will make anything you send them for reasonable pricing. Custom boards etc are not at all hard to manufacture, and for the amount of money you can get, of course you can team up with someone. I think the most people overestimate the cost of bespoke PCB creation.
Dangerous things sells implantable chips.
Eg. https://dangerousthings.com/products/apex-flex?Antenna=Narro...
Why do you think it's too costly? It's well known that there are divisions in DPRK that are focused on generating $ through crypto hacks and compromises.
We're dealing with reasonably sophisticated state actors here in this dark forest; not script kiddies.
Cheap $5 PCB + programmable small FPGA is a very viable route too for hardware implants; but even a microcontroller / ESP32/etc will probably do.