Should I use "one" or "it"?

Question

Which is correct:

I think I need a better kind of gun. But where can I get it from? I can’t find it anywhere in this maze.

I think I need a better kind of gun. But where can I get one from? I can’t find one anywhere in this maze.

Answer 1

Easy rule: If you're looking for "a" widget, then, use "one". If you're looking for a specific ("the") widget, then "it" is correct.

I think I need a bazooka. The shopkeeper has one but I can't afford it.

The last "it" is because we're now referring to the shopkeeper's specific bazooka, rather than ones in general.

I think I need the golden bazooka. The shopkeeper has it but I can't afford it.

Here it's a specific bazooka all the way.

Answer 2

Since you're referring to something non-specific, "one" would be better. If you were referring to a specific object, you would use "it".

I think I need the AK-47. But where can I get it from? I can’t find it anywhere in this maze.

Answer 3

In the context you provided it would appear that "it" is more correct if there is only 1 gun in the maze. If there is more then one gun "one" might be more correct. There is not a lot in it though, and both are acceptable.