monoprice.com has great prices on USB to USB micro cables. On ebay, I found great prices on the Motorola OEM wall chargers that came with my DX. Look for ones with 1 amp of output for the fastest charge time.
I also just bought on Amazon, a new USB cable with a right angle micro so when my GN is in the cup holder in my car, it does not need to be upside down. (UUSBHAUB3LA)