We would have to know the specifications of the chip, not just the size, in order to determine compatability.
I would recommend using a seller which guarantees Mac compatability as well as offers a lifetime warranty on their RAM.
If you do a search on the forums under "RAM," you'll find numerous threads which discuss choice of RAM.
From my reading, the 3 most commonly mentioned websites (in no particular order) are: www.datamem.com www.crucial.com www.macsales.com
All 3 meet the qualifications I stated above. On each of their websites, you can navigate to the necessary RAM by selecting your PB model.
I have had personal experience with both Crucial & DataMem and have had good experiences.