Try finding a Cherry G80-5000. Adjustable split keyboard. Haven't used mine in a long time, because it feels like I can't afford breaking or even just any kind of wear.
Seconded. Mine is labeled "MODELL MX 5000", and others are called the ErgoPlus, but they're all basically the same keyboard. I didn't realize what a high quality device it was when I bought my first one. I've now been coding and gaming on it for well over a decade, and it still works beautifully. Even the flexible plastic parts show no sign of damage.
The split angle is completely adjustable, from very wide to no split at all, so it will fit just about any shoulder width and can be temporarily collapsed for guests.
It has Cherry brown switches. I can feel when they engage, but they don't click, so typing noise comes mainly from the key caps bottoming out.
The numeric keypad is detached (and can be unplugged) from the main unit. This is great for right-handed gamers, because it can be moved to the left side of the keyboard and the mouse can be brought in closer.
I originally bought the Cherry 5000 because it was the most comfortable model in the ergo shop at a reasonable price. After a year of using it and a touchpad, my RSI issues were greatly reduced and I was able to go back to using a mouse. After a couple more years, my RSI issues were gone.
It's a real shame they discontinued this model, and not at all surprising that they sell for $500-1000 on ebay. I'd probably pay that much if mine disappeared. It's the only keyboard I've ever liked, and I expect it to last a very long time.