I suppose it depends on how much it owes you and how much money you want to throw at it. I'd give a couple of the garages Turboman listed and ask them for a rough estimate
Other cause for untraceable water loss are inlet manifold gasket ailed, and water pump, and fracked coolant bottle and faulty pressure cap, but looking at the amount of emulsion, the two suspects have got to be inlet manifold gasket, and head gasket failure