You're gonna have to look around on your own, it seems like.
I have absolutely no interest in the '80s, but when looking for anything, especially old-fangled clothing (which I look for A LOT), I first search MTS for the relevant phrases (in this case, 80s, 1980s, vintage, beverly hills, various famous 80s movies or people...), then check the following spots, among other places:
http://www.parsimonious.org/fashion3/ - Has a few things under dresses/outfits that look like they could be '70s or '80s, and some funky pants, among other things.
http://www.poppysims.com/index.html - Has a few things that could work, including an athletic dress.
http://www.all-about-style.com/sims3.html - Has a few things that could work. Corset dress; also, lots of things with shoulder pads, so.
Also, google is your friend, and the following:
http://en.wikipedia.org/wiki/1980s_in_fashion
... will give you a better idea of what to search for.
Look around, try to see what specific patterns or types of clothing were the most common, find those, and enjoy your '80s sims.