You will have to make an adapter; as there is not enough demand for what you want, for a manufacturer to make them. You will need trailer side connector, short piece of cable and a 50 amp 120/240 volt 4 wire receptacle. I would use a recessed range receptacle in a weather proof box if I were going this route. More than likely, if I did not want to cut off the connector I would just buy an extension cord.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7