Hi Vanci,
Attached is the product datashete from Kobelco for GTAW, ER-309LMO Filler.If you're in North America, feel free to contact their Houston Office.
You may search Metrode products also, datasheet B-51.Their product is classifed as SFA 5.9 ER-309Mo.But when you go through the datasheet you'll see that it's a Low "C"(Max-0.03%)filler.Possibly "C" is kept low for dual-grade certifiaction.
Metrode is represented by Euroweld, Mooresville,NC.
Hope this would help you.
Thanks
Pradip Goswami