You should not try to make your own Old Bay spice.
As Meg Favreau writes in "Table Matters," you'll need $50 in spices "just to create a product that you can buy, ready-made, for under $5."
And if you try to call anything that doesn’t come in that "classic, primary-colored tin 'Old Bay,' a roving gang of ardent Old Bay supporters (most likely from the Chesapeake Bay area) will hunt you down and force-feed you crabs until you show some respect for their illustrious hometown spice."
Scary! Read her article here.