You have to be careful if you get into non NEMA connectors. For example, in our theatre the state of NY decided to wire all the theatre lighting with a 20 amp, 120V/240 twist lock (
Example in the first row here) connectors. The problem was while it was wired for 120V in the theatre lighting circuits, the same connector was wired for 240V in the hallways to power floor buffers. Every once in a while a student would plug a theatre light into one of the hallway receptacles - very bright for a short time! Connectors such as these that use the different voltages on the same pins are no longer "official" but still sold an Non NEMA or obsolete devices.
While I don't know if your generator uses them, the NEMA L5-30 is the official 120V, 30 amp connector - See this
NEMA Configuration Chart. Not too difficult to find as an inlet & female connector since they are used by both the RV & boating industries as the method of wiring detachable cords. (
Marinco) is a good source (although expensive) for individual connectors.