Jason Oliver at TimeZone posted a message that the Speedmaster Pro owned by astronaut Deke Slayton was sold at some auction. You can find it here.
Here is a picture of the watch:
I hope the buyer puts on a new strap! 🙂 The buckle seems to be original Omega (and in the right time-period). I really doubt if I would ever sell such a personal belonging as a watch that joined me on spaceflights.