Laser Visual Marking of Objects in a Grid?

I have a grid of containers 20 x 100 in size that I want to visually "point" at one at a time with a laser. The containers are cylindrical with a 5mm radius with about 2mm of space between each container. Being able to draw an "X" on them with the device would be ideal. I'm not sure where to start searching for something like this. I've been searching for a few hours and have come across spirograph drawing, but I'm not sure that would be a good approach.

Any ideas on where I can start searching?

Why "X"? Laser pointers usually have holographic lens , stars , arrows, hands etc. http://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=laser+pointer

Does the laser need to be coaxial with the containers, or just illuminate the end? I'm wondering whether it is enough to pivot the laser to point at the right spot, or you actually need a 2D moving head to put the laser emitter in the right place.