I tried to talk them into hard wiring but they want the charger to be "mobile." I also am a little confused why it asked for a 14-50 receptacle but that is what they want(I think I said 6-50 in the OP but that was wrong)
Most plug-in EVSEs come with a 14-50P. Some can also be ordered with a 6-50. The 14-50 allows portable charging at campgrounds / RV parks.