The BMW oil made by Shell is also sold in the US by Avance Auto Parts and the specs seem the same, including made by Shell, so it seems to be the same oil. It's titled Shell Advance 4T Sythetic 15W-50 motorcycle oil and can be ordered from Advance's website. I don't know if they sell it in their stores. I'm sure it's considerably less expensive than BMW oil purchased from a dealer but don't know exactly how much.
The Mahle oil filters can be found on Amazon, etc.and appear identical to the ones Mahle makes for BMW, at a condiderable savings.
In the US our Congress passed a law years ago that limits what restrictions vehicle manufacturers can put on requirements that would nullify warranties, although I don't know if that includes oils. It does eliminate a requirement that service work, etc. be done by an official dealer for that brand. It's called the Magnuson Act and info can be found by googlling that title.