Hmmm, genuine parts are hard to come by for the average repairer unless they are either an Apple authorised repairer or an actual Apple store. Most of the ones you find on the web listed as "genuine" aren't. Best bet would be to have a look for local authorised Apple resellers as they may be cheaper than the Apple store repairs. That being said, I recently repaired an iPhone 4 with an unofficial part and it was pretty impressive, would take a very fussy person to tell the difference.