Isolation Transformer, Quick Pack, 56 VA, 2 x 115V, 16V, 3.5 A: Electronic Transformers: Amazon.com: Industrial & Scientific
24V 40VA Thermostat and Doorbell Transformer, Power Supply Compatible with Nest, Ecobee, Sensi and Honeywell Thermostat, Nest Hello Doorbell and All Versions of Ring Doorbell (Style 1) - - Amazon.com
Amazon.com: Endurance Pro EI Type Isolation Transformers PRI.120/208/240 V AC 50/60Hz 24 V AC 40 VA 4031F Class 2 Control with Foot Mount Replacement for Jard 4031F HVAC Furnace Multi Tap Packard
Isolation Transformer, 240 VA, 1 x 115V, 24V, 10 A: Electronic Power Transformers: Amazon.com: Industrial & Scientific
Control Transformer 40VA, Primary 120, 208, 240V Secondary 24V, HVAC Furnace Multi Tap - - Amazon.com
Dwyer® AC Power Transformer, APT-40-1DN, 40 VA, 120 VAC Input, Dual Hub: Amazon.com: Industrial & Scientific