I use two holsters for my Alaskan. One is a Simply Rugged w/o retention strap. The other is a Galco DAO with retention strap.
http://www.usgalco.com/HolsterPG3.asp?P ... &GunID=342
I picked up on of those last year. Its a great shooting revolver. I heard that Ruger sometimes has these special runs of this type of revolver for private security companies.