Don't buy used U bolts, they are single use only item. Mutual wheel, Inland truck part or any big truck parts house should be able to supply with new. There are several types of top bends, from U to squared off corners.
Might find what you are looking for here:
https://www.anythingtruck.com/category/ ... disp_order Midway truck parts in the Chicago area used to bend them while you wait, just bring them one to copy.
Always replace U bolts and nuts/hardware together.
Also, if the axle is sliding around then the locating "pegs" have been knocked off the axle housing. You can get by without them if you make sure the axle is located correctly before tightening the U bolts. You'll need to measure carefully to make sure the axle is centered and aligned with the frame. The locating pegs do all this for you automatically, but if they are missing than you have to do it manually. The pegs fit into recesses in the spring perch just like to bolt in the center of the spring locates the spring on the perch.