Earlier on I bought a very cheap (< 4 euros) PSP USB charger/sync cable, brandless, packed in a rectangular white box with the photo of the cable on it. But the quality is not so satisfactory, mainly for two things: 1) The AC jack is a bit too tight; 2) I notice some charging irregularity as the orange charging LED on my 3200 flashes sometimes, and may also not lit at all. After a very brief trial I decided to ditch it, perhaps i will give it to someone who has a real PSP.
Then a while ago I bought a new one. It's Logic-3 retractable USB charger/data cable. The jack fits into Z well, and charging does seem to work very well. Even though the price is a bit more than double of the other, I am very happy with this one, especially because it is used to feed my beloved Z' delicate charging circuit.
I've googled a bit and found quite a lot of sites are talking about the Logic-3 game console products. Looks like a decent manufacturer.
Although both cables are produced in China, I can really tell the difference, both in their look and their build quality.
Here is a photo of the two cables FYI.