Thanks for pointing out my mistake. I did the research, and know know the difference between the two (makes sense).
I did by the gun new, or so I assume. I purchased it from a retailer, in the box. As far as I could tell it looked new, still in packaging. I didn't know that you could insert the mag catch the other way. This will definitely work out in my favour as a lefty!
I will look into purchasing the metal catch and will Dremel as necessary.
Thanks to both of you for the quick reply!