Original OEM parts are available at Catalina Yachts. Kick-up rudder $455 complete, $351 blade only. Centerboard $475. Made of FRP from original molds. Not HDPE.
Based on what I saw at Catalina Direct, they don't have the OEM rudder assembly available, but DO list the Ruddercraft replacement, which uses HDPE for the foil. They do sell fiberglass rudder foil, and they do list a cast AL headstock, but say "Call for availability."
Based on the original poster's self-classification as a "low budget sailor," I don't think any of the options at Catalina Direct are going to fit that criteria.
Best case scenario he could hope for are cheap used parts from someone at the class association.
Or, for the DIYer, he could HOPE that Catalina Direct has the headstock casting and the tiller head, and possibly centerboard brackets, then hope that the class association has templates and dimensions for foils, then go and fabricate his own tiller and foils out of laminated mahogany (not plywood!) That would be the mid-price option. (Plywood is dimensionally stable, but the 90º orientation of the plies make it unsuitable for the side-loading requirements of foils. Even BS1088 is not appropriate. It's only 1/2 the lateral strength of lengthwise laminated hardwood.)
For the expensive, keep-as-close-to-original-ist, find a headstock and tiller head assembly used, then purchase glass foils. Because I think that "call for availability and price" notation on Catalina Direct is somewhat ominous.
Or, for the expensive, just-get-her-in-the-water-ist, buy the Ruddercraft assembly, centerboard brackets, and centerboard foil.