There is no one "perfect" sign for "pacifier." In general you are going to
have to mime the action of putting one into your mouth using either an "x"
handshape or a loose "G" handshape. Or you can tap your lips
twice with the front knuckle of the X-hand.
PACIFIER (version 1)
Use an "x" hand or a modified X hand:
There is another version that uses a loose "G" hanndshape.
I have seen people using a palm-back-"T" hand for the sign for
pacifier. If you see native Deaf adults in your local
area doing the sign, feel free to copy them. While
I sort of like the iconic (picture-like) aspects of that version I'm
not totally comfortable with it.