We dont have one. Our house didnt come with one but over the last 3 years we have gotten used to doing without it. If you rinse the dishes before you put them in thedishwasher I think that helps, I also think they are only wrthwhile if you are going to use it at least every day or every second day as I think the dishes sitting in there dirty would make it smell funny.

At my mums house we had this little lemon thing that hung off the dish rack inside the dishwasher that gave off lemon scent.