ISA has standards for drafting the sysmbols. I suggest you look at standard ISA 5.4 and 5.5.
If the symbols is not quite of what you are looking, I suggest call the manufacturer and asked them how other engineers have represented their Coriolis flowmeter.
In our office we use the venturi symbol as a flowmeter and then we indicate on the description of that particular flowmeter what it is. (magnetic, corilis, ultrasonic, etc., brand name and model number)