Broken thermostat housing

[FAT TONY]

so i was installing a temp gauge and when i went to put the thermometer thing it broke the housing i was looking at it and it was pretty rusty im not sure if maybe it was the rust or it might have not been the right size im thinking it was mainly the rust, i will upload pictures later but for now i was wondering if any one knew were i could find that part and if im using the right name, because i know the thermostat housing is the elbow looking thing that goes on top of the thermostat but the thing that broke is the one that holds the thermostat on top......... any help