TLDR: You get what you pay for. Any 5V charger will charge the device, you do not need a specific "Tegra Note Charger". The larger the current rating the quicker the device will charge. If the psu does not have a USB port in which you can plug in a USB>MicroUSB cable, ensure that the psu has a microUSB plug attached.
There are two main considerations though besides this, first is brand/quality, the second is the charge current available.
Brand/quality - Not all chargers are made equal. Most nowadays are switchmode but component quality and design will vary greatly between chargers of different brands. Whilst the basic buck design that most manufacturers will use is efficient, there is a lot of transient noise introduced as well as voltage ripple depending on the design and components used. The funny thing is that the difference between a "good" psu and a "bad" psu is cents in the dollar but many manufacturers will choose to save those cents. The sense behind it? Most consumers are completely ignorant.
Charge Current - There are two main differences you will see between a 500mA or 2A charger. The first is charge time - if the psu is capable of supplying a higher charge current and the device is capable of drawing that larger charge current then your device will charge quicker. Thing is though, the USB standard requires negotiation to be made between the psu and the device for charge currents larger than 500mA. If you buy a cheap psu that is capable of 2A but does not have the negotiation IC, you will never charge more than 500mA. Once again, the difference between having this IC and not is cents in the dollar.
