It depends on the holster, I'd say. The way I'll describe this, there are three types of holsters - specific fit, close fit, and universal.
Specific fit holsters are molded to the firearm itself, and they're not going to work with a different model. Kydex is a great example.
Close fit holsters are what you'll see in catalogs sometimes. This holster will fit several different models.
Universal fit holsters will be nylon, basically, and are just a place to hold a barrel and trigger guard. The biggest ones will fit anything, but you'll end up with more holster than barrel in many situations..
So, in that situation, you may find a close fit holster that will work for you, but I don't know as I've never handled a sigma. I know that High Noon Holsters makes nice leather and they make holsters for the sigma, so that may be an option that I'll vouch for..
Specific fit holsters are molded to the firearm itself, and they're not going to work with a different model. Kydex is a great example.
Close fit holsters are what you'll see in catalogs sometimes. This holster will fit several different models.
Universal fit holsters will be nylon, basically, and are just a place to hold a barrel and trigger guard. The biggest ones will fit anything, but you'll end up with more holster than barrel in many situations..
So, in that situation, you may find a close fit holster that will work for you, but I don't know as I've never handled a sigma. I know that High Noon Holsters makes nice leather and they make holsters for the sigma, so that may be an option that I'll vouch for..