I don't know where you will get them but you'd better be sat down when they give you a price for one offs. You might find a Chinese supplier on something like alibaba as they have a listing for everything on there if you look long enough.
HAHAHA not by any chance seen the fire pit domes? Plasma cut and looking bad ass!! From having been one of many that have asked and searched high and low, it would appear America is the place. They seem to be very easy to get hold of over there. In the uk however they seem to be as rare as rocking horse s**t