I put together a combined power supply/driver for relays with 24V coils:
The project is OSHW so feel free to have a few boards made if you've also got a big pile of scavenged relays with 24V coils! They're common in telecom gear which is why I've got a drawer full of them. If enough people are interested I can run off a bunch of them to save on board fab costs. In prototype quantity it's around $5 a board.