I have two rolling totes. One is a large Tutto, that I got for transporting and storing my Janome MC6600. It's not put in it very often but once in a while I have to put the machine away when we have company.
For my truly portable machine, I have one that I got at Joann's. My travel machines are smaller - I have a Featherweight and a small Europro. I like the standard size because of the room it provides. I keep a complete set of scissors, seam ripper, a few rulers, extension cord, a small cutting mat, a rotary cutter with blades, thread, and room for my projects I'm going to work on. I even have a spare light bulb for my machine. That way I don't have to worry about forgetting something when I travel.