The USB cables that come with the MP4 nano clones are pretty average. Mine broke after a week, and finding a replacement is near impossible.

However, you can actually split open the plug for the mp4 player using a kitchen knife.

Once you have got the plugs terminals exposed hack off the old shoddy cable. Now unless that plug is completely smushed it should be good to graft onto any other USB cable.

I used an old printer cable that was laying around, I chopped off the printer plug and stripped the wires. The connection points on the MP4 plug for the different coloured cables are shown below (most usb cables have these standard colour wires in them).



A quick bit of solder and superglue the plug back together. You now have a longer and more reliable cable.

clever*

If you are in the UK Maplin appears to sell a replacement USB 2.0 A to Mini B. I haven't tried one, but they look like the right thing from the picture. Only trouble is, at 1.5m, even the shortest one is a bit on the long side.