Inspiron mini power adapter tip polarity

hi there folks. I've got an Inspiron mini 10v which I bought early 2010 in the UK.

It still works fine and is my main computer for work, but the power adapter has broken. I've bought a replacement which didn't work, and a lot of googling tells me this is probably because the tip polarity is wrong.

I need a centre-negative polarity. I've started asking suppliers on eBay and Amazon if they can tell me tip polarity of the replacement they are offering, but so far the only response has been a general "they all work for Inspiron mini 10, 12 etc etc" which doesn't seem to true.

Does anyone have any previous experience of this, suggestions for where to get the right replacement, ways round it. At the moment my  net book is out of power with no way to charge it, so any suggestions much appreciated.

Thanks,

Andrew