For any of those who bought your own surplice and cassock, what website did you buy yours from? I want to buy my own that fits better than the ones they have at the chapel. 

You can probably just look around online, do some web searches.  You might actually ask your chapel where they got theirs or look at the tag to see if you can find the brand name, since there may be some slight differences in style that would become obvious if you're standing there next to a couple others wearing the standard ones.  Even if the differences are subtle, they can stand out side by side and potentially ruin the symmetrical aesthetic.

RJ Toomey is a popular maker of server cassocks.  Now, they do also make the Novus Ordo style ones ... but just pick out the Traditional looking ones.