Matchbox Lesney 67a Saladin replacement turret white metal casting.
Can you fit these yourself? Yes!
Just clean up any white metal casting excess with a small file to make the casting as neat as you require. Then clean / prep and paint the appropriate colour.
The model may need to be dismantled for this part to be fitted.
This can be inserted in a dismantled model and flared to retain it and allow for rotating. If you have an assembled model you might glue it in place.