Convincing parents for a......?

Okay so, I'm basically in love with ferrets. When I go to the pet store I always play with them and my parents just watch me.. I know a lot about ferrets, how much care they need, they're diet, etc. I've done my research. The only problem between me and ferrets are my parents. They think they smell.. and I don't know really, I guess that's the only issue. Well, they don't think that I'll take care of them. A few years ago, I had parakeets... and well, I didn't really take care of them. And a few months ago I had sugar gliders, I didn't really take care of those either.. So we gave them to this petstore. (It's not the kind of crappy pet store your thinking about, it was a good family owned one, trust me.) They got sold already, so I'm sure they're in good hands.. I just felt like Suggies weren't for me. I'm almost positive Ferrets are though! I went to the petstore today with my mom and dad, and played with one, but It was sleeping. Sometimes, at different pet stores, Ferrets have an odor, but it doesn't really bother me...It bothers my parents.. And it's only that bad because they usually don't bathe them, or take care of them that well. I really want a ferret, and I need some help with convincing them. I'll add more details if you have questions about this situation. Thanks in advance:)