I also use the round plastic containers that Chinese Take-out food comes in for mini sewing kits that I use when going to appointments. I can fit an embroidery project, the hoop,small scissors and all of the threads to finish it in one container. They are a little more substantial for traveling.
Re: the plastic containers - WD40 takes the glue off after you take off the label. Also, slip in a piece of cardstock (from the back of a greeting card) regarding the contents. Then when you change the contents you can change the label.