The BMW dealer is the only one that sells it. The oil is made by Castrol. I email Castrol and they confirmed that currently only the dealer sells the oil because besides racing cars only a few production cars in the market use that type of oil. I also email Mobil 1 and Valvoline and they replied saying that they do not offer that type of grade.
My 3 local BMW dealer sell the litre for $10.00. There are few dealer selling the oil at $8.50 but with shipping and handling it comes out to more than $10.00.