This is a quick draft of a foot for the "Sheet Holder Ender 3 - 235mm Plate Glass Spring Steel Mix".
Why? The glass plate is too heavy and I didn't want to create a Cults account ...
I am no engineer ... so just use some little drops of super glue. ;)
I took some measurements of the holder in PrusaSlicer, watched an 8 minute video about Onshape an spent an evening creating this foot. ;)
I added a lot of helping geometry, which was not used at all, to the bottom sketch and played around with extrusions, chamfers and fillets.
The author remixed this model. Imported from Thingiverse.
I designed a simple support foot around the holders end.