I happened across one of these antiquey letterboxes in Guineys (Dublin) recently. Can't remember the price, but Guineys is generally cheap. Not sure what the quality is like, but from a quick look-see it seemed okay.
Traditional Postbox - (TSH020Z) from the above link, exactly like the ones Iv purchased from supervalu for €10. First one lasted roughly three years as got a bit rusty on front but did paint over with bit hammerite so lasted another year. Have found BQ Woddies etc very expensive for the likes.