You can get pockets that are permanently attached to the suit, or you can get a MOLLE panel installed on one of both sides where a pocket would be.
From there, you can pick the pocket you want - velcro, zipper, whatever. I have one of each and I know that at least the zipper pocket has a small plastic D-ring inside. Because you can take the pocket off and play around with it, it's easy to add whatever you want to add.
The MOLLE system has been used on military and public safety gear for a while. It works well. The only drawback I have found on my drysuit is that the edges of the pockets aren't stuck to the suit so line can get hung up on the corners. You can order a suit with pockets permanently attached if that's as issue for you.
I picked up one of these a MOLLE dropleg panel from ebay so I can use my USIA pockets with a wetsuit during the summer.