DONT TELL MUM......we Need Help

Hello,
My name is Katie, and I am 17 years old. My mum is getting remarried. (we are so exited!)
Her dream would be to wear a Maggie Sottero dress. But she keeps saying "I just cant bring myself to pay `that` kind of money, I would rather spend it on `you` girls.
Mum is willing to give her dream dress up for us!
I have an after school job ........ So, we; my sister (13) my stepsister-to-be (10) and my stepfather-to-be, my grandparents and I, would like to buy her a Maggie dress as a surprise November birthday present!
Mum mentioned that it takes 16-22 weeks to order the dress and we dont have that much time.
I snooped around and found this site in mums favorites list. We were wondering/hoping that someone in here might have a Maggie dress for sale? It doesnt have to be new.
She is a size 10 (but she could get a size 12 altered). I found a list in a drawer that had 12 different named Maggie dresses on it, so we guess that she likes them all! We checked the site and most seem to be strapless, with A-frame, not much train, some ivory and some white.
Please email us if you can help.
Katie_jane7@hotmail.com
Thank you for reading our message.
Katie, Erin, Tamarrah, Jim, Grandy & Pop.
P.S. DONT TELL MUM!!!!