Original Red SD Memory Card Chamber Door Cover Part For NIKON D3100 Camera | eBay
New SD Memory Card Door Cover For Nikon D3100 With METAL & Spring | eBay
Amazon.com: SD Card Slot Cover for Nikon D3100, Digital Camera Memory Card Shell Back Door Socket Lid Protector with Spring and Iron Sheets : Electronics
Best Nikon D3100 SD Memory Card - Outside the Shot