If you're looking to buy a vibrator there are two main options: online and your local sex shop.
With the world of online shopping there's hundreds of different websites offering to ship a vibrator right to your door. Here is a list of some of the best places to buy vibrators:
SheVibe.com is one of the first places I start a vibrator hunt. They have a huge selection of vibrators, and some interesting brands you won't find anywhere else. They also ship all their vibrators in discreet boxes that have either "SV Inc" or "Bruce Banner" on the return label. Here's what it looks like:
The website itself has a cool comic book style theme, and at the top of each vibrator category is a little sex toy comic with fun vibrator jokes.
Lelo is a brand of vibrator designed in Sweden, and Lelo.com is the online home of their flagship store. By buying directly from them it's a bit cheaper, and if you're a student they also offer a 15% discount on top of that.