So the parts for replacing the valves are now around $80 on ECS but a pair of aftermarket (new) on Amazon is $13.86. Anything wrong with the Amazon (Dade) item - it has good reviews?
Dade Set of 2 Crankcase Vent Valve PCV Pressure Regulating Valve Fit for BMW 11127547058 14506018001
https://www.amazon.com/dp/B01H027CUQ..._4D3DEbZ0RF4X9