Hi I am old tinknocker when we, had this issue we put ceiling box and grill at the shower and ran ductwork to a inline remote fan to vent out to outside. I think the fans we used were fantech brand, I hope this helps.
Hello. I saw the pictures I just thought you might have a peter wright anvil, because of the mouse hole on the side. They forged and welded anvils, just a thought. Thank You sharing the pictures .