What to buy to replace a cracked glass or lens for my iphone 4s?

Please send me links or any suggestion about what to buy to replace a cracked glass or lens for my iphone 4s? I have couple idea on eBay,
this one xplosion-proof Front LCD Lens Glass Screen Replace iPhone 4 4S Protector White
or this one 12 Color Replacement Touch Screen Digitizer Glass Lens for Apple Iphone 4 4G 4S

I'm NOT So SURE,
MY PHONE IS FULLY FACTIONAL AND IT HAS ONLY CRACKED ON THE FRONT TOP RIGHT CORNER, EVERYTHING WORKS, JUST CRACKED, AND I WANT TO REPLACE IT, I DON'T KNOW WHICH ONE IS THE RIGHT ONE.

Well my answer is probably not what your looking for. I don't own one so I guess its
up to you. You could try craigslist to see if some one might be selling one or one
of the stores that sell them. I'm sure there are a lot of used ones out there