I bought a standard "Honda Motorcycle" key from a locksmith for about $3.
Then I cut the head off of the key to end up with just the cut portion of the key.
I took the end off of the right side grip (threaded onto the throttle shaft).
(If you replaced your grips, as I did, then this will be easy)
I used 2-part epoxy to glue the key into the grip end.
Let it set overnight to harden & you are done.

This is what it looks like when installed in the Ignition Switch:
 

Sorry for the dirty pics, When I took these, I had just been caught in the rain the night before.