I have mine in large A3 zip lock bags because they are see through but I also use the A5 size. These are small enough to put in my handbag and hold quite a few blocks worth of pieces, some folding scissors, a small snap box that once held Clover pins and in there I have a few pins, some needles and a bobbin wound with the hand thread.
I have about three of the A5 'kits' ready to go and always have one near me if I'm goinig anywhere. Now and then I have to have a bit of a re gathering to see where I am but it works well!
It will be interesting to see what others do and what ideas we can pinch from them!!