I OTOH, bought a Campag Euclid/Olympus RD from the era when Campag was trying to compete
in the MTB sector. then dropped the idea.. late 80's they were moving into close outs ..

Those were able to replace the pulley cage, and so found another one Medium cage ,

bought the long cage pieces from the shop's vendors .. Its on my touring bike, still ..
have the medium one to sell.. [inner and outer plate]

NB Shimano really makes just putting a whole new RD on, the More efficient use of the shop time ,
as their parts supply chain, through wholesale distributors, is whole boxed RD's .