I use a Primetime Petz wood pet gate to keep the pets out of some rooms in the house. Over time, the door latch was no longer able to keep the door closed, so we started using a loop of rope to hold it. I measured the door, the latch, and started playing with some shapes in Tinkercad to come up with a design that would work.

You may need to scale it a little in your slicer to get it to fit perfect as the first one I printed was a very tight fit...plus I didnt like the way it looked printed with the top down. I re-sliced it at 110% and rotated it with the top up and used tree supports under it. That made a nice finish on top and it fit very well.

I put 2 holes in the sides so i could screw it to the pet gate, but you could leave the screws out and just lift it on and off.