Buy replacement Sierra Electric low voltage remote control relay light switches & parts for an older home low voltage lighting system installed in the 1940s, 1950s & 1960s.
Sierra no longer manufactures their relays including the 7048S relay. Pass & Seymour makes a Sierra low voltage replacement relay that is quite expensive. The best replacement option in a Sierra system (if your switches have 3 wires) is to replace them with GE remote control relays. GE relays are also 3 amps at 24 volts AC-DC, and work with momentary low volt switches.
The GE relays will work with your existing tranformers. If you need to replace your transformers, you may use GE transformers as well. You are still able to buy Sierra style low voltage trigger style switches. Help guides and wiring instructions are available so you can shop with confidence for compatible parts for your lo-vo wiring system.