May not meet your particular definition of small, but my portable printer is a Voron 0.2. The frame is sturdy enough that you can attach a handle to one corner and just carry it around with you, at least for a while. It's not particularly lightweight. But it is small (fits completely inside the build volume of my other printer), and being fully enclosed within the frame, seems more durable than the likes of the other tiny printers (Lemontron, A1 Mini, etc.)