You should be able to buy pretty much any SATA hard drive and install it. It's as simple as switching the drives out and then formatting with the new drive once it's installed. Helpful guide here: http://www.cnet.com.au/how-to-upgrade-your-playstation-3-hard-drive-339282375.htm
The pictures are for the older style PS3 so if you have the new one it'll be a little different, but I bet you can figure it out. The procedure's the same, but the HDD is in a different spot on the new one.
Good luck!