have & have got

[Fine Tree]

A: Why don't you buy this one?
B; Oh! [_______].
1. I have one.
2. I already have one.
3. I've got one.
4. I've already got one.
Are these all natural in the brackets? I think all are fine but #1 is somewhat unnatural. Am I right?

Thanks in advance.

[Rusty]

A: Why don't you buy this one?
B; Oh! [_______].
1. I have one.
2. I already have one.
3. I've got one.
4. I've already got one.
Are these all natural in the brackets? I think all are fine but #1 is somewhat unnatural. Am I right?

Thanks in advance.

They are all OK. In sentences without "already" we tend to put more stress on the verb. I have one. I've got one.