There are lots of them out there and prices range from super expensive OEM to low price on Amazon. The best advice I've found is to get a rebuilt one from your favorite auto parts store with a LIFETIME WARRANTY (warranty covers the life of the car). The price is in the mid-range but it's the last one you will ever need to buy for your car.
Also, check out the YouTube videos and see how it is installed. The best way (in my opinion) is to have your favorite mechanic install it with a lift. It can be removed/replaced from underneath the car by lowering the AC compressor (3 bolts and an electrical connector) without disconnecting the lines.