Why pay $30 for s small shelf when I can make one from IKEA draw fronts ?
Besides, it's too small to put my hard drive and iPod.
1 - Any stock pieces no more that 6" x 18" IKEA draw front are ideal.
Lots avail in the as-in bins.
2 - L brackets
3 - Zip saw & belt sander
Measure out notch of 4" x .5. Cut out with zip or scroll saw.
Another notch if you need to run cables
The iMac stand is ~ 20 degrees angle, and 15" tapered
Use belt sander to bevel all edges, else the shelf will not be level
Take an L bracket & bend it slightly to match the iMac stand.
Screw on the shelf edge, but not too tightly.
Now put shelf in & swing the bracket to meet the iMac stand.
If all is well, shelf & bracket should be flush.