This is under half the list price, but still expensive. I'm tempted to buy it to see if the metal case has enough shielding effect to be worth the price, and return it if it doesn't... but I've spent a lot recently and the odds of success probably aren't better than 50%. The touchpad isn't shielded at all, and they are usually pretty noisy. On the other hand, you could easily put a metal cover over it.
Not sure why that would be any better than a vintage PS/2 keyboard, as the USB connection alone will likely make it more intolerable. Also it looks like it has a display built into it, another negative.
Also it looks like it has a display built into it, another negative.
That's the trackpad, and yes, it's probably noisy.
That company makes keyboards in both PS/2 and USB. I don't know if the controllers are interchangeable (like the ones in the later Chicony 2971 series keyboards), but if so there's a good chance that you could cannibalize a PS/2 controller from one of their cheaper plastic keyboards.
And you might be able to disconnect the trackpad also. If you look at the photos in the ad, it seems that it's designed to be disassembled and worked on. The screws on the back aren't hidden under labels or rubber feet like most consumer keyboards, and the USB cable is connected with a threaded metal cord grip that you can remove with a small wrench.
I'm planning to do something very similar, but I'll be living in an RV for a while and it needs to be a little bit smaller. I'm looking at using a combination of shielding and distance, probably starting with a Chicony keyboard.
For anyone interested, there are at least two other makers of much-cheaper metal keyboards that can be ordered in PS/2 with either no pointing device or a trackball:
I saw one USB OIT Q9000A (trackball model) for $55 on eBay, but it sold.
I don't know if they will help, though. The holes for the keys are pretty big, and aluminum and stainless don't do much for lower frequency fields (see Merializer's tests of mice).
What I like about the DSI keyboards is that they're designed to be bolted directly to the surface they rest on. So I could build a metal case for my motherboard and put a small projector and a fiber transceiver and a big battery into it as well so that there would be no metal wires leaving the case (and no 'dirty power' or humming HDMI/USB/cat-6 cables).
I have a aluminum body mechanical keyboard, and at least for me it was worse than the cheap plastic keyboards, though both were still really bad. I even tried the optical usb cable and wired it to use a battery via a usb connection and not the power cord. It was better for me the first day I used it, but each day after that it got worse, such that in a few days it was no improvement at all!! If you wish to try this I can sell you mine half the price of the new one let me know. (This is the one I have https://industrialcomponent.com/opticis/opm210003.html)
I built my keyboard/mouse so it is 4 feet away overkill on purpose since I wanted to be 100% certain I would have no reaction. You can test how far you can sit from them to figure out the smallest length to make one.
the terminals / converters near both ends of the opticis-cable have to be shielded, preferably in a metal case or otherwise with layers of aluminium tape, as these produce a lot of emfs.
and yes of course indeed the powersupply needed at the desk-side should be clean DC.
apart from no shielding, what would make things even worse is to have other cables placed in the vicinity of these terminals.