Found that this part was broken so I'm needing to get another, any idea what this piece is called?? It goes between the bolt and the adjustment screw.

 

As suggested in your other thread, contact Rolling Thunder.

 

just what you said, axle adjuster. that one can be repaired if need be.
center punch the barrel where the stud broke off as close to the center as possible, make sure it is a good dimple. pilot drill the dimple with a small bit. determine the correct size you need (measure the other side) and drill the pilot for tap size and tap the hole. you can get a grade 8 stud or use a cut off bolt thread (sae 8) and thread into hole till flush on id and then weld it on the outside, will not take much since all you need to do is prevent it from backing out. no welder?? the try super duper thread lock of steel filled epoxy on the threads.

have fun!!!!!