Buy them online. You can find many contact lenses that can glow in the dark. And they are varied in different colors and designs. I just saw some such contact lenses at http://www.bodyjewelleryshop.com/online_store/glow-in-the-dark-contact-lenses-1202.cfm. Here, there are glow contact lenses in different colors. Good luck.
Some people tend to wear the strange contact lenses in different themes of parties. If you want to buy the dark contact lenses at a suitable place, you could go to the online store to have a look, instead of the eyeglasses stores. You could go to the walmart to have a look. There are many kinds of contact lenses there. You could go to have a search.
Well, it seems that you are planning to get some contacts with special effect right? As far as I know, that type of contacts are rarely seen on the market. But there are always new stuff on the Internet, maybe you can browse through the Internet, or some websites for online shopping to see if they are on sale. Amazon, Ebay or Best Buy are good options for you.