Found this at my local RONA, clips on my CXS like a classic systainer. It comes with a variety of cheap bits, but has two inserts with plenty of expansion room. It doesn't have t-loc locking knob. $69.99.
The front clips are hard to grasp when locked, but the sides are fine so you do those first and push the top systainer back.
The front clips are hard to grasp when locked, but the sides are fine so you do those first and push the top systainer back.