Hello... A much better option for those of you with lost or broken, but valid, copies of Windows 8 or 8.1 is to order replacement media. In your case, there's no reason to pay full price for another copy of Windows 8 or risk being infected with malware.
If Windows 8 came preinstalled on your computer, and you did have DVD or flash media but now it's damaged or lost, contact your computer maker for a replacement. Depending on their policy, your computer maker may provide you with Windows 8 media for free or a small fee.
If you legitimately purchased and downloaded Windows 8 from Microsoft, you can download Windows 8 or 8.1 again here, so long as you have your product key documented.
If you purchased a retail Windows 8 DVD, you can contact the Microsoft Supplemental Parts team and request a replacement.
While not a replacement for Windows 8, please know that you also have the option to create a Recovery Drive for Windows 8 using a friend's Windows 8 PC, all for the cost of a small flash drive. Your Recovery Drive can be used to perform all the diagnostic and repair functions that a full copy of Windows 8 can. See How To Create a Windows 8 or 8.1 Recovery Drive for instructions.