You can normally get complete replacement Wilkinson saddles (provided none of the lock-down screws have rested in place), though sometimes it's easier to replace the whole thing. Look for VS50 replacement saddles. But the Wilkinson post thread sizes have varied over the years, so if you go for a similar bridge, you may need to keep the current posts unless you feel like replacing the inserts.

I had a rusted Wilkinson bridge on an 1993 guitar I was doing up for a friend. Tried WD40 soaking but nothing budged. Ended up replacing the old VS100C (semi-locking) bridge with a WCS50 II and a Hipshot tremsetter. One had all imperial, the other all metric, threads.

Or you could fill in the two existing post holes and fit a six-screw trem instead. Or a generic 2-post trem to keep costs down.