How do you plan on carrying that pistol?
A simple kydex paddle holster can cover a lot of different applications without having to give away a day or two worth of your paycheck.
Good leather is awesome, but it comes with a price and a break in period.
If it is an everyday concealment holster that you are going to wear inside the waistband, it will need to be sturdy enough that it doesn't collapse on itself after you draw the pistol.
If you are looking for a good holster setup that is mostly for range use, your choices will also need to change.
I personally don't like "buttons" for retention but if you have to have an ALS with a button, I'd look at one of these...
http://www.safariland.com/products/h...1.html#start=1
...I use one at work with the M17 Sig and I don't hate it.
If I am buying it with my own money, I prefer Galco over Safariland.
Again, how and where you want to carry the gun have a lot to do with what type of holster you should be looking for.