It is unfortunate they went out of production in 1985. Every once in a while, one will show up on one of the auction sites, but as a general rule, people who have them don't let them go. The GP100 (the model that replaced it) is also an excellent gun, but you would never get me to swap my Security Six for one.
There are a lot of good choices for someone looking for a new production revolver. The GP100, any of the Smiths, one that is often overlooked is Taurus. I really like their Tracker series. My 4" .44 Magnum is a Tracker. The Ribber Grips that come stock on them are probably the most comfortable recoil absorbing grips I have ever used. There is one more revolver I will probably get and that is a 3" Taurus 692.
Of course, the Gold Standard for revolvers is the Colt Python. Colt just brought them back into production. I have not shot one of the new ones yet, but the originals had actions that were smooth as glass.
Thanks for the offer of the Hogues. I have always liked their grips and have them on just about all my handguns except my Glocks and that .44 Tracker. I do have one 1911 with Pachmayr grips. That is a 70 series Colt Commander