If you are talking about front wheel bearing you'll have to buy whole thing, they are not separatible.
It depends what year is your vehicle! I suggest you to go to the AUTOZONE web page and there select SHOPPING in the lane(after they ask you for zip code) you type wheel bearing and that's it, you'll get the price on the screen!
For my 2002 Sunfire it costs 65 bucks for the cheapest one! Part # V513017K
Good luck