ok.. its a long bolt with a "head" that is like a large washer.. the washer slips over the axel to pull it..
i've made these from .. guess what.. a washer and a bolt ..
cut an appropriate bolt's head off, cut a shallow slot in the bolt's end and weld an appropriate washer on there.
They do get bent up .. they are kinda thin and weak and are not meant to hold any weight or to support the axel or anything.. and the threads get stripped all the time too..
If you find or make one or can straighten the one you have, use care and use the banjo only to adjust the wheel position.