This is a simple extension for this thing: https://www.thingiverse.com/thing:2622035 by ermenegildo.
I found I needed a bit more space for glue sticks, pliers etc. and as I'd already printed the tool holder I just designed a simple add-on. It just sticks to the tool holder with a few drops of CA Glue or sticky pads if you prefer.
Toolholder_extension.stl | 12.6KB |