SOLVED: Girl and mother have kit that can create animals [s]

[Ellie]

I'm looking for a book - I'm pretty sure it's Young Adult Fiction - about a girl who I think is either just living with or travelling around with her mother. Her mother has a briefcase which contains a kit that can be used to make small mammals. They keep making them, and they die. The girl and her mother get caught by someone, soldiers maybe, and are sent to a camp. They have to keep this animal-making kit a secret. I'm sure they're in a snowy setting, too.

Thank you to anyone who can help!

[Ellie]

Ha! Typical, really. As soon as I post this I manage to find the book. It's "Siberia", by Ann Halam.