M17X Graphic upgrade for my pc i have a (NVIDIA GeForce GTX 260M) want to get a good replacement for under $200 links to product very much appreciated

hi i have an Alienware M17x

and i have an issue where when i turn it on the screen will show different colors for a second aprox each color so i an thinking the graphics is probably going out after about 30 minutes of powering off and on i can get it to work properly but its a pain

so i am looking for new graphics to replace it with for under $200 

the graphics i have is

NVIDIA GeForce GTX 260M

links to pages for graphics would be very much appreciated too