Hawthorne's use of symbols is so abundant that the only place you really have to search to find 4 is in the first chapter.
Look at the fact that this little prison is in a cemetery. Could you not argue that a term in prison is like a death sentence because you may no longer live freely in a society? Likewise, the door of this prison is made with the heaviest wood and iron, elements also used in the greatest executional instruments made throughout time.
The rosebush next to the door presents the beauty of a rose, the color of both love and blood, and the pain of a thorn. This rosebush represents Hester's life. In fact, the author identifies it as a symbol himself in the last sentence of the chapter:
It may serve, let us hope, to symbolize some sweet moral blossom, that may be found along the track, or relieve the darkening close of a tale of human frailty and sorrow.
The Scarlet Letter A should be your most obvious representative of a symbol because the red A means she's a sinner and an adulterer at that.
I think if you were to look further, you would take a look at Pearl, the Minister, or the Physician. Isn't it interesting how many times Hawthorne gives these characters labels instead of references to their names? Pearl strikes me because to become a pearl takes years of agitation by tiny little grains of sand. So for Pearl to become who she eventually comes seems to take much agitation. You could use most any uncomfortable situation she was in for each of these... including her first moments with her mother on display in the public meeting place.