I'm going to get glasses today and need to know where to get prescription costa lens

There is a store locator on the Costa site, just enter your zip code and you will get a list of local places that sell them...I got a pair last year, they are worth every penny.

i got prescription ray bans, they were pretty expensive...

Your eye doctor can install your prescription lenses in frames you already have.  Find what frames you like and buy them on Ebay if you don't have any.  I saved a bunch going this route and the lenses are at least as good as the Costa lenses they replaced.