I'm sure someone with more metal working experience than me will say this won't work but I see 4 parts in that pulley assembly. The pulley, which you would have to buy and the arm which you'd make from three pieces. I reckon you could but bar of the right diameter for the pulley and the machine holes then you just need to fabricate the arm. A scrap of steel, hacksaw and file would probably be enough. Drill and tap the bar and bolt it to the arm, a weld would be better if you have the facilities. Would be an interesting little project.