A quick Google shows that this type relay requires about 150mA at 12VDC...so the coil resistance is 12v/0.150A=80Ω. Assuming the contacts open at about 8V...about one time constant...it would require a 12,000µF/25VDC cap across the coil. And a diode between the +12V supply and the top of the parallel coil/capacitor.
You might also want to add a low value resistor (1-10Ω) in series with the diode to limit inrush current to the capacitor.
Haven't tried it, but it should be within that range.
Ken