case for all the bits and speaker

[DavidC]

I have ordered a big plastic box to put everything inside. Will see how that works.

I realise that if the battery is also integral, then I'd need some method of switching the power on and off (instead of just pulling the USB plug out).
I came across a USB to micro-USB cable with a switch in it, rated at up to 2 Amps. Many examples of which here's one.
http://www.ebay.co.uk/itm/Micro-USB-Power-Supply-Chargings-Cable-With-ON-OFF-Switch-150CM-For-Raspberry-Pi/112175217593

It's too long, and there may be shorter ones available.

Has anyone tried one of these?

An alternative is to physically break the cable and fit a rotary or slider switch of some sort into the box case, which might be a more robust longer term solution.
There would be a chance that a rocker switch could easily be switched on inside your flight bag and drain the battery unintentionally.

[JCurtis]

I realise that if the battery is also integral, then I'd need some method of switching the power on and off (instead of just pulling the USB plug out).
I came across a USB to micro-USB cable with a switch in it, rated at up to 2 Amps. Many examples of which here's one.
http://www.ebay.co.uk/itm/Micro-USB-Power-Supply-Chargings-Cable-With-ON-OFF-Switch-150CM-For-Raspberry-Pi/112175217593

No idea what they are like, but they need to have 20AWG cable for for the power lines as a minimum to prevent voltage drop that will cause problems.  I'd ask the vendor to state the cable AWG and the cross sectional area in mm² and see what they say.  Never ask if it complies with this or that, they will always just say yes regardless.

Note that for AWG the higher the number the thinner the cable, so the lower the number the thicker the cable.

[Richard]

David
  I have tried one of those, I had power problems with it. So if you get one it may cause you a few for you, you take your chance.