Pop the old knobs off with a small flathead screwdriver. These snap into place.
Included STEP file for minor edits.
Printed with a .4mm nozzle with .08mm layer height. May also work well with a .2mm nozzle!
Prints well on the base with normal supports and a brim like this:

For stronger layer lines, you can also try rotated 90° with tree supports like this:

Note - the little tabs can sometimes break off when removing the knobs. The knobs still stay in place just fine, but if you're concerned about very small children pulling them off and/or trying to eat them - you probably shouldn't use these.
The author marked this model as their own original creation.