I saw an article in Hemmings online that listed a place that rebuilds center links for Cadillacs. I don’t know anything about them but you might try to call them to see if they might be able to help you. Rymals Restorations in Grand Haven, Michigan (616) 846-6030.
Looks like Rare Parts in Cal seems to be the people to rebuild them. I have had 3 people contact me and they send them to rare parts. I will let you know how I make out. This will not happen till June.
I saw a center link (drag link) on ebay today if you’re still looking for one. Right now there is about 6 days left on the auction. Looks to be correct by the photograph.
Here’s what the add description says “1963 OLDSMOBILE F-85 STEERING DRAG LINK NOS. GM# 5677800. This is a New Original GM Steering Drag Link Correct for the 1963 Olds F-85 and Cutlass. The Drag Link has some paint loss and has acquired some Cosmetic Rust over the Years in Storage at the Dealership but Is New and in Good Condition. Great Hard to Find Item for your 63 F-85 Restoration.”