This is my version of a 6 inch holder.
As always as an engineer, I recognized a problem and wanted to solve it with extreme solutions.
Of course, once again I wasn't satisfied with what was available so far or what I found...
either it didn't fit well or something else.
I then made the part from scratch. It fits perfectly for 6"/150mm sanders.
All sharp edges are removed. You can now simply slide in from the top without getting caught on an edge or anything.