We have a system of shelves that we brought with us when we moved to a new apartment now. However, some of the bolts broke and now we're having a hard time buying new ones. These are not from Ikea.
Please see the image below.
The length is about 1 cm and is used to support some other metal holder below the shelf. I can provide more exact measurements or pictures if need be, but somehow I'm not able to find anything that looks like it in stores or online.
I do apologize about the low quality of the first image, it's all I had at the time. Now that I'm home, here are some more pictures of: 1) the initial bolt I was asking about 2) The thing it is supposed to support, installed already on the shelf. 3) Another type of screw of this system whose head I do not recognize.