GMC Sierra factory wheels are available online at eBay.com, OEWheelsLLC.com and WheelsAndCaps.com, as of 2015. All the wheels sold at these sites are original equipment manufacturer parts that are the same as the GMC parts, but possibly branded under a different name.
When shopping on eBay, looking for OEM GMC Sierra tires is the only way to ensure the parts are genuine. Other parts are available on eBay, too, but caution is necessary unless the listing says they are OEM parts.
All the wheels at OE Wheels LLC are OEM parts, but the customer must ensure the wheel fits a Sierra. This website lists the wheels for GMC all on the same page, and not all of the wheels fit the Sierra. This website, which also features reviews for the wheels, receives an A+ rating from the Better Business Bureau.
Wheels and Caps carries GMC Sierra OEM wheels from 2005 to 2011, and all the wheels match the original wheels on all Sierras. More than 25 models of GMC Sierra OEM wheels are available to choose from, and it is possible to read reviews before purchasing these wheels. This site also receives a rating of A+ from the Better Business Bureau.