The Canon 550D while released a few years ago is now very good value secondhand and would make a great second camera. It has a smaller shape than cameras further up Canon’s prosumer line and is good for people with small hands. It’s also light, so is not a huge burden in a backpack. The standard kit lens is not the sharpest and we recommend replacing this when you can.
The 550D is still available from resellers on Amazon or you can look at its successor the 750D.