Getting a playmate for 7 month old cat

I have a cat/kitten who is 7 months old and is absolutely crazy with energy. We feed her high quality food which has had an amazing effect on her as opposed to the quiet little furball she was when I first adopted her. The thing is, I'm gone much of the day to work and/or school. Not any abnormal level of absence, but the typical working adult hours, and whenever I come home she is very excitable to the point of becoming a little destructive for attention, and ignores the cat furniture that she clearly enjoys in favor of sleeping in front of my bedroom door at night. I feel like she's very lonely and also doesn't have enough to do to work off her excess energy, despite being spoiled with a variety of toys and would like to get her a playmate. I've done a lot of research (including this forum, thanks!) which indicates that the best age for a playmate is one approximately the same age. However, all of the postings I've seen for adoptable cats in my area tend to either be much younger (proper kittens) or much older (adults >1 year). Given her energy level, it would seem best to err on the side of younger than older, but I'm unsure what age should be the lower limit of that, and to a lesser extent, the upper limit of age above her. She is very warm and affectionate, but also has a tendency to bite as part of play, and appears to be disposed towards wrestling. I am concerned that too young of a kitten may be in danger of her harming it by accident. At the same time, I want a playmate who can "keep up" with her and accept the playing for what it is and play with her back. An energetic little furball for my energetic little furball such that they can blend into one self-contained furball to the benefit of everyone. )