If you're just looking to mount a few accessories to your new Sony A7s (A7/A7r) camera this new SmallRig Half Cage should give you that added flexibility. It might even be a good little half cage for other small cameras as well. Retail price $62 dollars, but if you pre-order now they're offering it up for just half the price at $31 dollars (click here).

Sony A7s Cage PreOrder