Anyone at any age can wear a diaper for bladder protection. There isn't nor should there be any age limit for it to be acceptable.
No one will really notice if you're wearing a diaper if you're concerned about that.
Wear a diaper if you need too. Don't let others keep you from living your life just because they might make fun of you wearing a diaper.
Lots of people have to wear diapers for protection. Wearing diapers isn't just for old people or babies.