Your best bet is to buy a good stand and get creative and build yourself a shelf that clamps to the first tier. I used to use a large piece of wood that extended out so they keys could sit in the front and 2 electron boxes in the back, secured by clamps I bought at a hardware store.
This looked awful but worked well. I built a shelf, but ended up using it on my desk and my monitors and a rack sit on it, mixer below. Companies sell stands for AKAI MPCs that would fit an Elektron Box or two. Look into that.