(13-inch, Early 2011) Buying memory/RAM from non-Apple vendors?

I've read somewhat similar threads here, and I apologize if I'm beleaguering the issue - I just couldn't find a comparable match...

I have a MacBook Pro - 13-inch (Early 2011), and I'm needing to up RAM/memory (see below screenshot).

Processor 2.3 GHz Intel Core i5

Memory 4 GB 1333 MHz DDR3

Software OS X 10.8.2 (12C60)

I'm a student and don't need a rocket boost here, but as you can tell, I probably needed to upgrade the day I purchased the Macbook...

SO. I'm wondering what my most cost-effective options are.

Apple sells a memory module that I *think* is compatible with my MacBook, at an "impressive" $200:

Apple Memory Module 8GB 1333MHz DDR3 (PC3-10600) - 2x4GB

I found the "same" listing on Amazon for $32.50:

Apple Memory Module 8GB 1333MHz DDR3 (PC3-10600) - 2x4GB

and (similar-ish?) on Newegg for $44.99:

Patriot Memory Mac Series 8GB (2 x 4GB) DDR3 1333 (PC3 10600) Memory for Apple Model PSA38G1333SK

I'm hoping, with a promise of sending good karma your way, that someone can help me crack the case of how to give my Mac some TLC. RAM(?), memory, Apple, reliable external vendors... hey, I'll even send you cupcakes if you give me your address!

Thanks so much!