My DD will be Baptized next month, and her name is Aria. I have been told that I have to find a Catholic name for her to be Baptized with, but I do not agree with that! Her name has roots in Hebrew and Italian, and Angels also sing Aria's. Please could someone help me find a convincing argument to take to the priest as to why I do not need to choose a Saints name for her to be Baptized with?!
There is no convincing argument. The priest's judgement is final, and if yours takes the view that appropriate baptismal names are Biblical or Saints names, there isn't much you can do about that.
Your options would be a) go to a different parish where the PP has different views or b) add a suitable baptismal name (there is of course also c) abandon plans for baptism but I'm assuming that, as you wish for Catholic baptism, omitting this sacrament isn't really an option).