I have 2 small machines that I take to classes - Janome 720 and the Janome Gem Gold. I've even taken the Janome 720 on plane trips as a carry on. The Gold has more stitches, that's the only difference between the two.
When you get a light weight machine, I suggest you buy some of that rubberized non skid shelf liner, you can find it in the dollar store. Cut a piece and stick it under the machine, that will stop it from moving around.