I ran into the same problem. I spoke with the fellow, George, who owns MPG Mopeds in Merryfield, VA. He told me that blanks were no longer available. He suggested to me to see if I could get a locksmith to put a new lock on the ped. However, he said it would be a better investment to get a lock and chain that couldn't be cut with bolt cutters, because merely locking the front wheel for the ped will not deter theft that much. You could just pick up the ped and put in in a car or truck. With a chain&lock you can at least lock the ped "down" to something "secure". Anyway, his suggestion sound good to me, so that is the route I went.
Rich