I just sold my Catalina 30 this spring. About 6-8 yrs ago, i replaced the bearings in my furling drum. I also replaced the plastic shim things. Since everything is stainless , aluminum or plastic, you need to thoroughly run fresh water through it. Squirt it in from the bottom or anywhere. This will clean the crap and spider poop out. I would never use WD-40 which will just cause it to gum up.
Next, when I sold my boat, there was a tupper wear or some plastic container with a dozen or more spare rollers. You might try contacting the owner. His name is Mark. There also may be a copy of the literature on board that he can copy for you. It might be in the book with papers and manuals.