I made an earlier post about a great shoulder bag for carting lenses and stuff around during the dayviewtopic.php?f=48&t=6427#p67471
Here is the case I am using to take my NEX kit when travelling from point to point. It weighs 4.25kg with everything in and its dimensions are well within those which qualify it as a second carry-on (handbag / laptop) bag for British Airways. It cost £22 at Maplin.http://www.maplin.co.uk/aluminium-flight-case-3991
As you can see it enables me to fit in quite a lot, specifically a NEX-5, NEX-7, external mic for NEX-5, 2 batteries, E 16/2.8, E18-55, 2 LM-E adapters, Rokkor-M 40/2, Leica Elmarit-M 90/2.8, Voigtlander VM 28/2, Voigtlander VM 25/4 and Voigtlander VM 21/4 and Zeiss ZM Sonnar 50/1.5. That lot should cover most bases!