Where can I find new charger cables for my tablet?

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I have a Chinese made 9.7" Onxyx Calypso tablet and I'm looking for a charger cable for it. One end must be a USB plug and the other end one of the round plugs.

After a HUGE amount of searching (!) I found this in Australia:

http://picclick.com.au/5V-AC-home-wall-charger-Power-adapter-For-291612453703.html

Brand new Input: 100-240V-50/60Hz Output: 5V 2APin Size:2.0mm x 0.5mm Compatible for: 5V Adapter Wall Charger ALDI,ONIX,Pendo,Unisurf,Target,Thomson Tablet PC

And I measured the pin on my current charger and it seems to be 2mm.

I don't need another wall charger, I need a USB - pin connection so I can recharge from my powerbank if (when) the power is out.

Thanks!!!

 

[Cybersurfer]

What about this?
http://www.hdcabling.co.za/10-in-1-....html?osCsid=b4bf9aa02b23ed6732563acda052411d

 

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I have one very similar, and I don't know why, but the 2mm plug which does fit, does not charge the tablet for some unknown reason. It goes in, shows it is charging, but isn't.