How can I fit a trap on a sink bowl that's directly above the vertical drain pipe?
Is there a joint under that escutcheon? 

If so, why not run an elbow toward the back wall, then  an elbow upward to a vertical pipe, then an elbow forward to a conventional p-trap?

This would effectively reduce the risk of siphoning water that an s-trap creates.



If there is not enough distance in back of the pipe, the whole elbow/p-trap thing could be canted to one side or the other.

One or more joints could be eliminated if you can find a run of pipe with an integrated elbow. The lower horizontal run is needed only if the elbows don't move the vertical pipe far enough back to accommodate the p-trap.