The CEO of Silph Co. will give it to you after you beat Giovanni at Silph Tower.
You can find it in Silph Co. (received from the President of the company). Silph Co. is the big building in Saffron City.
Try to catch it with a masterball. that's what i did.
Save Silph Co., Just like in Blue.
Team Magma Hideout
professor elm gives it to you..
You find it in the team aqua hideout.
from your enemy teams base
You can only get one
In team aqua's hideout
you have to deafeat Giovanni in the silph co. tower in saffron city
u buy it for 1000000
The professor gives it to you at a certain point