I have something like this in a regular small lower cabinet for cookie sheets and pizza pans. I know I got it at Walmart it the aisle with the dish drainers and cabinet organizer stuff and it has little plastic clips to screw it into place. Wire divider

Maybe file folder organizers from Staples?

I have this one it isn't very deep but it works really well.

http://www.bedbathandbeyond.com/store/product/mesh-pot-and-lid-organizer/1042452553?categoryId=10558

I use the metal file folder organizers for pans in my less-than-standard-depth, narrow cabinets. You could screw in an inverted U thingy to hold it in place, if you want to. I didn't, because the cabinets are only 11" and I can't get maneuver in there.

You could turn one of these sideways and make it taller than longer. http://www.containerstore.com/s/12-tray-divider/d?productId=10004540&q=tray divider

https://m.bedbathandbeyond.com/m/product/org-vertical-mesh-organizer-rack/1040864457

the wire divider Nicole posted a link to should work fine for this. the outer point part of your cab doesn't need to have the divider in it - just the mid to back part. that outer point part will be useful for a longer items(cookie sheet, serving tray) to 'expand' into. It will still stay in its part of the divider. Then put shorter items on the shorter side of the cab - like a cake pan or cutting board.

I use those wire dividers in a drawer to hold lids, cake pans etc. Some items take up more space front to back than others do. It's ok, nothing wiggles out of the wire part holding it. I store my mesh wire strainer (with a handle) in the back where some items don't expand into...

The chrome Rev a Shelf tray divider would fit. I have one on the bottom of my cabinet and one on the shelf like you are planning.

https://www.rev-a-shelf.com/p-225-tray-divider-u-shape-sink-and-base-accessories.aspx