Unless you're teasing grizzlys a .357 is all you need.
That being said the .45 Colt is just about my favorite round. If you roll your own it will give you all sorts of fun.
.44 mag will be a bit less expensive if you're buying over the counter.
The Ruger Blackhawk is probably the less expensive choice.
Try some on for size as far as barrel length is concerned.