To start with, I would consider putting wood shelves on the brackets, and then put the speakers on the shelves.

If you make the shelves the right size (large enough), they will give you some flexibility in the exact speaker placement.

If you want stands, I suggest the SANUS Steel Foundations stands. They make a 22 inch stand, which might work.

They are rigid and solid, which is ESSENTIAL in a stand.

They also have a center column that can be filled with lead or steel bird shot, which adds mass and improves your speakers performance.