Changing coil voltage for Electric Relay - HF14FW/0XX-HSTF
Short of magically coming up with a replacement, there's nothing that's ideal. You appear to have a "sensitive" coil unit nominally 620\$\Omega\$ coil resistance @23°C. 

Using a 12V sensitive coil unit with a series 130\$\Omega\$ 1/4-W resistor will draw 50% more current so it could damage the driver or overload the power supply. A 24V one might sort-of work, but fail with a bit low mains voltage on a hot day (pick-up voltage increases as the coil warms), and would have shortened contact life. 

Other similarly  rated substitutes such as Panasonic are typically much less sensitive in coil current so they would be much worse than the HF14FW/012-HSTF + 130\$\Omega\$ 1/4-W

There is one more-or less sure way, if you have a good set of tools and patience and can know enough to be able to take care to avoid possible safety issues, and that's to buy a replacement sensitive coil unit of any voltage and graft the new contacts (the part which will have worn out) onto the old coil. This kind of relay that meets VDE and not just the more slack UL specifications has a plastic pusher that works through a hole in a plastic barrier. That separation is critical to safety. 

If the machine isn't too expensive, I'd be inclined to try the HF14FW/012-HSTF + 130Ω 1/4-W personally. Note, not the HF14FW/012-HSPTF