These things have been lifesavers for me. Having zips replaced is really expensive if you wear H and M jeans, as I often do. The new zipper costs more than the jeans did! Slipping zips don’t often happen, but my favourite jeans are now about 12 years old and the zip is starting to slide down.
I used to keep the zip up by putting a safety pin just underneath the slider. It worked perfectly but was a real pain if you needed to go to the loo. It was also noticeable.
These are really good. You can make them yourself if you are so inclined but it’s much easier to just get one or two of these. You just slide the loop over the button. It’s not noticeable and there is no extra fiddling. I have them in pale blue, white and black.