Erm, I seriously suggest that you don't try to obtain strontium, for several reasons. For one, it is almost ridiculously reactive to oxygen and water, so is usually found with other elements. Two, your body absorbs it like calcium, but instead of calcium, your bones are weakened by it to the point that it is the reason for bone cancer.
However, if you insist...
You will probably find strontium in a factory that manufactures telivisions and computer monitors. Both of the two use Strontium and Barium oxide to produce the best looking images. So if you feel in the mood to walk into a Microsoft factory and go steal a whole bunch of Strontium, be my guest. Otherwise, the only way you'll ever be able to see it is if you go and actually try to mine it at a mineral mine.
But on the rarity of those, just let me put it this way: If you find yourself in Northern Mexico, Central Spain, Midwestern Turkey or Eastern China with a pickaxe, gloves and protective clothing, go for it. You'll probably make a good thousand bucks.