You will have to get them from a wrecker. No body repops them that I know of. I switched my shock mount bumper for the 73, early 74 bumper and recessed it to get rid of the rubber space filler. You could use the 75 bumper with the 73, early 74 brackets (still need to get from a wrecker), but you would have to drill new holes to mount it. The spare holes could be filled with bumper bolts and still look fine. I considered this before I found the nice 73 front bumper I ended up using.
Cley