2005 Chevy Uplander Broken fan knob

My children broke the fan knob (knob to the left). I still have the knob, but have no idea on how to go about fixing it and have found nothing on the internet. Do I have to replace the whole climate control center or just the knob? Where can I buy the parts I need? Is this something I can do myself? I am pretty handy. ;) Any info would be great. Right now I have a screw controling the fan but I am sure it will strip itself out eventually. Thank you!