My children have those toy-watches. They are made of cheap plastic and break easily. It is so sad to throw them away because of a defective buckle. So I tried to make a replacement myself. This set is useful for 14mm watchband, which looks common in toy-watches.

This is a first (and likely the last) version. It may seem raw and rude, because yes, it is.

You may want to add a drop of glue at both ends of the rod to fasten the buckle. But you are gentle enough, it does move that much.