Where Can I Find a Copy of These 2 Old Games?

Where can I find and buy a copy of: Halo, and Halo 2? (I have a Game Stop, but they don't sell original Xbox games anymore.)

I've never really got to play them cause I didn't have an Xbox (Had a Ps2) and I would really like to play it through the beginning and learn what really is going on instead of playing it from Halo 3.

Suggestion:

Try getting them on Amazon.com
Thats weird the gamestop by me has halo 1 and halo 2.