Only the more expensive “split” oil filters are now available from BMW, and this as a kit only for about $24 each, excluding shipping.
The “split” filter is made for machines fitted with oil coolers which seem to be in the minority. (I’ve never seen one, but then I’m no expert!)
The “straight” filter is obtainable from K&N Filters, Their part # KN161, for $7.98 each. My local Napa Auto Parts ordered in for me and shipping for two filters was a further $10. Admittedly this doesn’t include the all-important white “O” Ring. This can be ordered separately from your usual BMW supplier @ $1.97 each. Part # 11 421 337 098 According to the airhead “boffs” this used to be referred to as “the $1000 “O” Ring”, because of the rather spectacular consequences if it didn’t seal properly. Now with the passing of time and inflation it is “the $3000 “O”Ring”!
Moral of the story. DO replace the “O” Ring with a new one every time you change the oil and the filter.
PS Owners of older British bikes please ignore this advice. Your bike doesn’t even HAVE a filter and anyway, with the way they all leak oil,they don’t need a filter because the oil is always fresh!