From the ExpoImaging YouTube Channel:
Jeff Rojas demonstrates how to easily create a dramatic, hard-lit portrait with 2 flashes and a few Rogue 3-in-1 Flash Grids. Flash photography lighting video tutorial, techniques and tips.
B&H carries the ExpoImaging Rogue 3-in-1 Flash Grids. For a slightly less versatile (but less expensive) option, you might consider getting the Opteka OSG18 1/8" or the OSG14 1/4" Universal Honeycome Grids and a Honl Speed Strap.
Update: After creating this post and getting it ready to publish to the site, I decided to try and recreate the results with the gear I had at home (I don't own the 3-in-1 grid, but I do have the Opteka grids linked above). Here was the shot I came up with:
Trying to replicate images you find intriguing is a good way to gain experience. Ultimately, you learn a lot from the process and the lessons learned can help you work more efficiently when executing your own creative ideas.
By the way, this is your first glimpse at my new studio space. You'll likely be seeing more of it in the future.