Can I get empty iphone and ipod cases to practice replacing the screen?

I would like to replace a friend's iPhone screen for them instead of sending it to Apple where they might look at some private photos that are on the device. I have some technical ability, and are A+ certified, even if that won't help much with apple devices, and i am just looking for a method of practicing replacing screens without the posibility of damaging a $500+ phone. Latest Generiation or one previous is prefferd.