Does Apple provide white iPhone 4 back cover OEM replacements?

Hello all,

I'm looking for the original iPhone 4 white back cover replacement for my iPhone 4. I have ordered two back covers from eBay claiming that they are OEM covers, but they are not. The lens is smaller on the ones they are selling on eBay and its not as crisp as the original lens when taking pictures. Does Apple sell back cover replacements? If so, how much do they cost?

Thanks and take care,

L