All The Currently Available, Lego Compatible, Train Wheel … | Flickr
3D Printed LEGO® Compatible Steam Wheels, Big Boy Pack – Brick Train Depot
LEGO Pennsylvania Railroad K4s Pacific completed. It's slightly oversized for 1:38 or 1ft≈1stud scale due to plate-height-compatibility of the driving wheels and articulation clearance for the pilot wheels, but it's close enough. :
Amazon.com: LEGO Parts, Bricks, and Pieces - Black Train Parts Combo Pack (2 X Buffer Beam with Sealed Magnets and 2 X Train Wheel RC, Holder with 2 Black Train Wheels) : Toys & Games