How to save up for a bag?

I REALLY want a Louis Vuitton Speedy 25, but I'm bad at saving. I only get �10 per week, then about every 2 weeks, I babysit and get �25 ontop. But then ofcourse I've got to buy clothes aswell. And I need clothes because I'm going to france next month, Italy soon after then New York so I'll be spending loads of money there, and buying clothes for holidays. My family's pretty alright for money but my dad won't pay �425 for a bag he says, and I'll have to earn the money myself. It will take me ages to save. Any suggestions on how to get money and save up? Because pretty much I'm always going like to the trafford center like every couple of weeks with my auntie, and shopping with my friends, so I'm always spending my money and I don't get that much :( Any suggestions?