This is an accessory I made for my carrier after my cat injured his nose on the sharp edges of the carrier grate.
I printed this out of TPU on my ender-3 pro although you may able to print them in more rigid materials as long as they don't break during assembly.
Print in the orientation displayed in the figure, with supports.
After printing, attach to grate and, if necessary, ad a bit of glue to make sure the caps don't fall (I didn't use exact measurements and so I left a bit of a clearance).
Since this was designed with FreeCAD, you can have the source file to modify in case you need it.
Also, remmember that the part is not symmetric so, you'll need to mirror it in your slicer for half the parts you need.
The author marked this model as their own original creation.