I bought a used MacBook Pro but it's missing the extension cable. I use this a lot and would like to buy one. Apple Stores don't sell them. I saw some on ifixit and ShaggyMac. ifixit's are used and ShaggyMac's seem to be new, but are these ok to buy? I know it's an extension cord but I don't want to risk my new MBP over saving a couple of dollars. I've also seen some on Amazon but not sure about the quality on those. Some guy took apart a duck head prong thing and showed the poorer quality when compared to the Apple branded one.