Battery breast-pumps (double) for working outside?

[InFrance2014]

Hi,

Quick question- I've decided to buy a breastpump to feed my 4 month old while I go back to work. Some of the time I can direct-feed during the day, but other times I have to pump. Main issue is I won't have power supply during the day (I will be on fieldwork and at conferences), so need battery pump.
I am used to a rented Medela Lactina which is good but needs power (and is huge). I don't have a massive milk supply so need something decent in quality and speed.

Can anyone recommend a decent transportable battery-powered double pump that is under 200 quid?
I was tempted by 2nd hand Medela Pump In Style but it's not closed system...

Thanks in advance!

Ardo Calypso. I switched to that from a Medela Swing when the Swing wasn't up to the demand when I went back to work. The Calypso also has benefit of being a closed-system (so much more hygienic and you can sell or pass it on with a clear conscience after you've finished with it)

I bought mine directly from the Ardo website.

Seconding the Calypso, I love mine. Haven't used it with the batteries but I assume it would be as effective.

I've used it with batteries. It is slightly less powerful, but that wasn't an issue for me as I didn't use it on full whack anyway. It's a great pump

Thanks for advice everyone, husband bought a Medela Swing Maxi already.
Although I did research the Calypso, will check that one out if I don't get on with the swing.