Nest thermostat needs power supply

[PicatN]

I listed this as a nest thermostat 2, but neither the box nor the thermostat says anything other than Nest Thermostat.  I bought the Nest Thermostat and now it shows I need a power supply with a C wire. Where can I get one of these?  I can’t return the thermostat since it’s already been installed , but I wasn’t told I needed this additional part before I purchased the thermostat. Any help you can offer would be greatly appreciated.  All I can find are articles on how to install the power supply and how to check if I need one, but not where I can get one. 

[Patrick_Caezza]

@PicatN 

It sounds like you have the Google Nest Thermostat (2020), it comes in various colors and has a mirrored display.

How do you have it wired?

Can you post a picture of the original thermostat's wiring if you have one?

What type of system do you have? HVAC, Furnace, Boiler, or something else.

How many wires are used for the thermostat?

[PicatN]

@Patrick_Caezza, I have a furnace. I don’t have the original thermostat, but there are two wires to the thermostat location. 

thank you for any help you can give me.