Need handle of some sort on cap windows

We have a cap on our F150. Opening and closing the side windows is somewhat problematic as one of us either has to climb in and push the window open/closed, or apply enough pressure from the outside (flat-palming usually) to slide it. Our fear is that either my hubby or son will push a little too hard plus it's a PITA. We were in the hardware store tonight looking for a small knob-type handle that we could stick on and use that to push/pull with. Any suggestions or is there another way to open and close the window with ease? Thanks.