So I have an old Columbian 331/2 vice. Picture below. It came to me with out a base. I have searched eBay and Craig list but no luck. Any suggestions for getting a swivel base?
Looks like you would need not only the base, but also the center bolt, and the lockdown.
In this area, that vise (with swivel base) would sell for ~ $25. It would likely be much more cost effective to get another vise, rather than attempt to acquire the swivel base and associated parts for yours.
That said, you might get lucky posting this up on the GJ Vise Parts Swap Thread: