Should be checked warm not cold see if its up then, Coolant can be bought off ebay £26 for 5 litres concentrated delivered.
Have checked it cold, warm and hot, still on the low marker.
Is this the coolant you are referring to
http://www.ebay.co.uk/itm/Chill-Factor-5-Litres-Antifreeze-and-Summer-Coolant-RED-for-Lexus-LS430-/200915900345?pt=UK_Vehicle_Oils_Lubricants_Fluids&hash=item2ec78557b9
its genuine toyota £26.73 thats the one