One spare key in my jacket pocket. Another in the front compartment on the RT. I'd have to break into it or disassemble the fairing.
At one time, I bought a spare-key velcro pouch and velcroed (sp?) it in place on the gas tank near the steering tube. It eventually came loose. Probably a combination of engine heat and dirt.
I keep a spare key in my wallet. Duck tape keeps it from falling out. However in Sedalia, I lost my wallet, and cell phone in my tent. The same day I lost my key at Walmart. It seems when you are juggling 3- 4 things at the same things it is easy to lose one.