Where can I get the driver update for AMD Radeon HD 6490M on Mac?

I've searched everywhere (to my knowledge and google results) and can't find anything at all. I'm finding people asking about it with BootCamp, but I do not want to Bootcamp my Mac. I already have VMWare Fusion so It's no use to do it. There's a problem with one of the 3D shaders and from searching I need to update it but I can't find the update. Recently(for the last 4 months), this has been affecting my production software as well, thus, my work in turn. I'm getting really frustrated. I need to get things moving again immediately.

My Mac information:

Mac OS X Lion 10.7.4

15-inch, Early 2011

Processor 2 GHz Intel Core i7

Memory 8 GB 1333 MHz DDR3

Graphics AMD Radeon HD 6490M 256 MB

Can someone give me any answers please!