The cheap music stands sold by Lidl have an extension to support wide sheet music parts. Unfortunately that extension bar tends to sag, thus not continuing to offer support. This T-shaped piece holds the extension bar in the correct (horizontal position).
The stl file is for the right-hand side. You need to print one mirrored along the X axis to generate the left-hand side. Use black abs to match the black color of the music stand.
Update: fixed a detail in the center, and added the Google Sketchup file.

Cannot generate correct gcode for this stl file with sf35.
I tried different settings but there is always a problem, either with an incomplete layer or printing in the air. These problems are reproducible: you can see that the gcode is wrong when using a tool such as Pleasant3D.
When I accidentally made the hole in the object too large (first attempt) there was no problem. When I lay the object flat on the base for printing (rotate in repG) there is no problem but the object then lacks strenght.
When I remove the hole (in Sketchup) and print the object without hole there is no problem either...

This is a derivative of thingiverse.com/thing:8939 which I made because the original was too small to actually hold AA batteries after printing this on a ToM.
The bottom part was redesigned, the top is just scaled from the original.

This type of terrace roof is popular here (the Netherlands) and so are the hanging plants. Unfortunately the hooks don't work well with the edge of the terrace roof, so I created an additional hook that fits both.
Note that when the hook is hanging down the bottom part of the hole is curved to better fit the hook of the plant hanger.
Design was done in Sketchup. Simple design but very useful thing.
It is probably thicker and thus more sturdy than needed, but overkill doesn't hurt.
The image is sideways because thingiverse wants all images to be in landscape orientation.

Just created this filament guide which mounts on top of the ToM, using the screws that hold the back z-rods. (The screws are long enough.)
This is especially useful when you have a filament spool located behind the bot.

The supports for an accordeon tend to break after some years.
There are (unfortunately) several types. This one is for larger (conservatory) instruments.
Note that the hole for the screw is not in the center. There are two possible pieces which are a mirror image of each other.
These pieces are available in accordion parts stores but seldom in stock and stores are few and far between... so unless you live near Castelfidardo in Italy making your own piece is easier than buying it.
This was created in Google Sketchup.

Lidl (supermarket chain in Europe) sold cheap (10 euro) music stands that appear pretty good. Unfortunately some of the plastic parts tend to break. This piece is a replacement for the connection between the upright pole and the part that holds the sheet music.