These old systems are rapidly becoming obsolete. I believe the relays are a GE type but the switches are very hard to find. The problem you will have is that were wired on the job site in one of two ways. 1. There are relays install at each ceiling j box and that would control the light in that room. 2. There would be a central relay panel that all the relays are there but the problem can be that there may be a central switching point in a bedroom that you can turn any light in the house on. There panels are usually a mess.
The relays are a latching type which the push on latches it and push off unlatches it.
You can convert these monsters by installing a standard toggle switch and a small continuous duty relay to replace the tubual type. I have had to do this a few times and at some point these will need to be changed out
You can porbably use off the shelf pushbuttons or SPDT-Center Off switches in place of the original switches. I seen a home electric book from the 1970s (from Time-Life or the like)that have the GE system fully defined.
I had those GE RR-7 relays in my old house in Md. IBM Gaithersburg used them everywhere and the maintenance folks gave me a bunch of them. The real problem with the original switches was they would bind on the cover if it wasn't perfectly aligned and the relay coils would burn up. They will not take a continuouis "pick" shot. They are pretty nice for things like your outside security lights because they can be controlled form an unlimited number of locations. I ended up designing my own system here using CMOS and solid state relays. It basically works the same way but only requires a SPST momentary contact switch ("D" flipflop). The added advantage is I have a delayed power on so my motion detectors will not latch on in a short power hit.
In Europe latching relays are pretty common for lighting in locations that would normally require 4-way switching. They exist with both 230V control voltage and 12V control, the "switches" are ordinary bell buttons. I guess in absolute emergencies the 12V 50 Hz would work on 12V 60 Hz too. The relays exist for box mounting an DIN rail panel mounting (the latter would be useless in the US).