[Angua]

Try googling, quite a few sites came up on search "wrought iron gates". Wierdest thing is with gates is they still are sized in imperial whereas most things are now metric. I am presuming the size you are after is the gap between the posts if so you could possibly get a 3 foot gate and have wooden posts (just a thought).
Alternatively do you have a reclamation yard in your area? They have all sorts of odd sized stuff (you may need to clean, de-rust and paint whatever you find but chances are it will be fairly unusual).