金丝熊 is easily available from local animal markets in my wife's home town. We asked the owners of different stores and they say it is not a mouse.
So what exactly is it, is it just a fancy name for a mouse or something else?
Officially, it is "Mesocricetus auratus" (Golden hamster) (source1 source2). It belong to "仓鼠科", and it should a kind of "鼠类" in Chinese.
However, as not everybody is a biologist, and as the name for it is "金丝*熊*", it may not be treated as mouse in everyday life.
Another reason is that "鼠" does not carry a good meaning in Chinese. It is often related to "stealing" or something alike. So it may be avoided to name a kind pet animal. (However, we do have "仓鼠" for pets.)
btw: To be honest, I've never seen a real "金丝熊".
According to Baidu Baike, it's a Syrian Hamster or a Golden Hamster. I'd say it's safe to say it's a hamster.
Hope that helps!
England had wartime food rationing until 1953, I think it was. We had a garden large enough to keep chickens, and we traded eggs with neighbours. A family who bred rabbits were part of my parents' circle of "We who get by, but only through hustling like crazy."
I remember when the Tories came back in and lifted the rationing "provisionally," and I resolved to go and buy as much chocolate as I could possibly scratch up the money for. I think it finally went away "in celebration of the Coronation" of Elizabeth II.
Anyway, mention of a not quite identifiable warm-blooded animal reminds me that one thing a war will do for you is get rid of all the rodents.