Just trying to figure out what might work for one.
I'd use Cat, Small. A full grown raccoon can get up to about the size of a medium sized dog, although I've seen stuffed ones that were as big as a german shephard. So about the same size as a lynx or small cougar. They tend to be stronger than dogs (which is why hunters usually use 2-3 coon dogs in a hunt, so one doesn't get overwhelmed). They tend to be smart as well (2 Int), and those opposable thumbs are handy for lock picking once the companion hits 3+ int.
EDIT: Obviously you'd need to remove the claws and give them opposable hands instead. Probably an innate bonus to disable device (+3 seems reasonable).