How do I convince my parents to let me get pet mice?

I've been trying to get a pet for the past like 4 years. I had rabbits before and they were perfectly happy until one ran away (had a hutch outside) and the other just died of old age. I really want something similar to that, but not as expensive. I've been doing some research and I would really like a few mice. The problem is, my mom totally hates the idea of me with pets. She thinks I will kill them and she will have to pay for everything. I wish she understood that I'm willing to save up my money to pay for everything. I would surely be very careful and shut the door when I played with them. I already cleared off space for a 10 gal. tank, to hopefully give her a hint. I've been really stressed out lately and I think having a little companion would help a lot. And my mom says I spend too much time on the computer, and I would definitely spend more time with the mice because I'm a super animal lover! My birthday is also coming up in a few weeks. Does anyone have any suggestions on how I can increase my likelihood of her letting me get them?