Relay adaptation of AM/FM Commutation

[FoKale]

Hi forum, I am trying to replace the AM/FM commutation swich on my Grundig SO390, which went bad because of a broken bar (made of dreadful alpax) The broken bar used to transfer the movement of the fm key to the commutation switch in a flip-flop manner which i can no further explain without drawings. Anyway I decided to convert the whole mechanism into a switch and relay combination.
The question is, how can I derive the DC voltage for the relay to operate? (It is a 24V DC relay) Is there a way to obtain the power from the unit's circuitry, (a point to take the voltage safely and drop down to 24V ) or should I construct a separate power supply for the relay?
I came across this solution for the same problem on the same unit (grundig SO390) but there was no explanation on the website and my emails didn't get a respond. (which is normal considering that the website been last updated in 2002 )

Any idea will be much appreciated, Ferhat