I need this screw for assembling my BabyBay baby cot.
In this manual, it is part number 1122.
This headless screw called
screws
Related Solutions
Looks like you need an 8-point socket. It is hard to tell the size from the picture but it looks small, you will probably need one in 1/4" drive. If you want a driver for it, you can get a 1/4" drive socket drive handle.
M5 Pan head machine screw.
Edit: M5 screws have a 5mm shaft.
Edit2.1 (my apologies): This is an M5-0.80 screw. 0.8 refers to the thread pitch, which (for metric screws) is measured by dividing 9.6mm by 12 threads, which equals 0.80. The picture above shows a minor optical illusion of 12 threads over 10mm (pitch = 0.8333); but M5-0.85 screws simply don't exist.
Best Answer
In my neck of the woods it would be a "set screw". You may not find one with the exact cross pattern in the top (most are Allen or slotted), but it should still work. The important parameters are diameter and thread pitch.
I don't see those values specified in that document, so some trial-and-error may be required. If possible, take the part it engages to a hardware store and test with common screws for size, then look for a set screw with the same diameter and pitch. A properly-fitted screw will turn easily until it snugs against the surface below.