I think Hafele does make a bracket, but I do not have confidence in it. How much weight do you expect the shelves to have to hold?
If you visit my web-site, you will see a winery that we did and on the back bar wall, you will see shelves jutting out holding wine glasses. These shelves have no visible support. There is a mirror behind the shelf.
I had the Contractor put steel "L" brackets on the wall, behind the drywall. Actually, here there was no drywall because the mirror covered up the brackets. The brackets were 2" x 3/8" steel, bent on a 90 degree. I got these from a local welding shop. Make sure they are bent on a perfect 90. Sometimes they are not. I also had they drill and counter sink for screws. I have them drill and counter sink for screws on both legs. Make them universal if possible. We then made the shelves with a pocket and we slid the shelves onto the brackets. I have done this many times and it is safe and it works. I also do this for floating counter tops.
If you do this, one thing that I have found helps is to make up a temporary shelf and attach it to the brackets, it can be a piece of melamine and ask the contractor to mount the brackets with the shelf attached to the brackets. This way, the brackets will be level and the brackets will not be twisted.
I hope this helps.