I have a Lyman 450 that broke the same link a year ago. I called Lyman and they said that I would have to upgrade to the "new" 4500 sizer so that the parts would work properly? It cost me $45.00. What I got was the exact same link that I initially wanted and a bunch of screws and nuts and a new handle with the redesigned round ball head! Looked at the invoice that they had sent me and got the part number off of it. Went to flea-bay and found one new for $16.00!
Now I have to get another one as I just broke the link again last night sizing 580gr .512'boolits!