ok just to clarify, is it the insert (bushing) that goes into the hole that is worn out/cracked and allowing the door to sag, or is it the actual hinge that is cracked. if it is the hinge like Ramblin Reflect came up with in a google search is what you want, if it is just the plastic insert bushings that's worn out you can get new kits to fix them also (I have to do my freezer door this winter and I did my refrigerator door two seasons ago.
once again you need to know your refrigerator make and model then a simple search or call to a rv parts store will get you what you need. in the mean time a couple strategically sized and placed washers can get you by in a pinch to level out the door, until you get the proper parts, if that is the issue.
here is the insert bushing so you can compare https://getrvparts.com/dometic-2931171066-refrigerator-door-hinge-bushing/