There are many helicopter and other air tour operators in the area:
- South Canyon
- Grand Canyon Tour
- List of various Grand Canyon Tours
- Papillon Tours
- Grand Canyon Helicopters
I could go on but I think this will do for now.
I would suggest talking about a tour like this when you get a to a hotel in LV. Reason being is that tour operators may be offering discounts to your hotel's guests but you won't know until you talk to a concierge. Online booking is always there but discounts may not be. :)