If parts are not available from the mfgr. then from what I see it would be relatively easy to make new ones by someone versed in simple fabrication.
If what I see is decent then it could be done on a table saw and drill press.
There may of course be something I can't see that might be best done on a milling machine.
THe damage done to the arm inside would not likely be a problem. You just may need a spare set of cheek plates and replace them every bunch of years.
Your local boatyard may know of a decent fabricator. Any boat railing and boat rigging fabricators around your area? They often need to be able to do simple fabr. jobs.