The first two links are right, those are what I got. The picture for the cable is misleading, the one we all actually received was the (much nicer) one above.

And yes, at first I was a bit miffed not to find a "Y-cable" already fitted with a mini-B USB plug, as they do exist. OTOH, this one is very short, which is a quality for use with the 770, and harder to come across. Moreover, those Pearl USB adapters that bend every which way are actually more practical than a cable that sticks straight out of the tablet's bottom connector, especially when sitting in the desk stand...

Karel, this is the one you need (male A to male mini-B) :
http://www.pearl.de/product.jsp?pdid=PE3324

Andrew, I don't think female-to-female couplers will do in this case.

A bit off-topic, but another fun "solve-all-your-USB-problems" gizmo at Pearl's (they do have a wealth of connectivity stuff) :
http://www.pearl.de/product.jsp?pdid=PE1386