That's an IEC inlet... I think OP is referring to something specifically intended as a generator inlet, like this: https://www.homedepot.com/p/Reliance-Controls

That's an IEC inlet... I think OP is referring to something specifically intended as a generator inlet, like this: https://www.homedepot.com/p/Reliance-Controls-30-Amp-Power-Inlet-Box-PB30/202213702 https://www.homedepot.com/p/Reliance-Controls-30-Amp-Power-I... Not impossible to get, but certainly a bit more expensive.