The easiest way to connect the motor would to buy the cord set from Sew-Classic and put a modern plug on the end of the wires from the motor to plug into it. That style of cord set has been around since at least the 1950s.
Sundial wire sells vintage style plug ends but they're polarized. You would have to file one blade down to fit the outlet block from Sew-Classic-at least they don't look polarized to me.
Unless you're there in person to check if they fit, trying to match the existing connector would be a guessing game at best. Better to either do the first suggestion or buy a set of connectors if you want it to keep the vintage look.
Rodney