Ya, it has been there for awhile. I think CobaltDragon got himself confused in relation to that, because what he linked was the standard sized battery in slim format. What you guys want if you don't want a more bulky battery is the Slim Extended Battery that, as xanthias has pointed out, is still in development.
Innocell Slim Extended Life Battery
In regards to price, buy a cheap cover, buy a cheap set of ear plugs, buy a cheap screen protector, but for the love of god don't skimp out on the battery. You really want to put a questionably made battery into your phone??? From EBAY?! Cosmetic items don't really harm the phone, just change the appearance. That battery goes inside your phone! Seidio is known by blackberry users to be an extremely high quality product maker.
That is just my advice, take it or leave it. As others have said in this thread:
You get what you pay for.