Rudders can be; resurfaced, refaired, & or re-profiled. As in changing their NACA foil section (profile aka foil shape). And if you need tips on any of the above, folks here, & via the provided links, are happy to offer up a hand.
For resources on rudder hardware, pretty much any shop which does custom machining should be able to help you out. And also, to further pursue your current
line of thinking, try a search on here via the header of chainplates. As lots of guys have links & info on getting new ones made, & the tech. is pretty much the same.
PS: You may find some helpful resources on www.L-36.com
especially regarding foils. But you can also try www.forums.sailinganarchy.com
for both too.