What are the dimensions of the standard Nokia power connector?

Here's the problem. I recently bought a Ziplinq USB charger, which
works perfectly for charging my phone from the USB port on my
notebook. What worries me is that I have to use the DC to DC booster,
whice means I have a very large assembly plugged directly into the
power connector on the phone. It's just waiting to get knocked and
broken, IMHO.

What I'd like to do is get a short extension cable, not for length,
but as a way of mechanically disconnecting the charger from the phone.
Nobody makes such a thing, so I figured I'd build it myself. Except I
don't know what size connectors to get.

It looks to be either 2.5 mm or 2.1 mm o.d., but I have no idea the
i.d. of that connector.

Any ideas?

Any pointers to where I can buy one?

Thanks in advance.