Well - I'm late to the party here. I don't have exactly what you are looking for, but I want to add to the topic for anyone coming across this in the future.
Attached are some images of the dividers in a T-Loc III. So this is the prior generation with the prior dividers (its what I have on hand at the moment). There are three sheets. They are about 4 mm thick. Could be PVC, but more likely ABS. Easy to assemble and insert, in the proper direction, so the lid closes.
Your idea to put these in the M 237 ToolBox is an interesting one. I'm going to out on a limb and say it won't be easy. With the ToolBox, there is the top piece which overhangs the systainer beneath it. If that makes sense. So I'm thinking these won't slide in.
[attachimg=1][attachimg=2][attachimg=3]