For service and parts needs, visit your dealer/retailer.
You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Accessories and ModificationsChevrolet Cobalt Service & Repair Manual. Front Side Marker Lamp Bulb, Replace
1.
Remove headlamp bracket assembly.
2.
Rotate marker lamp bulb harness electrical
connector (1) counterclockwise to unlock from headlamp assembly,
Fig. 1.
3.
Remove front side marker lamp bulb
(2) ...