What do you have that needs the brackets? There are probably sources for new stuff but I don't know them.
If it is a large C-band prime focus dish you can find those in the wild...OEM is easiest but you can adapt non-stock polar or H-H mounts to almost any dish if you have the gumption.
For smaller Ku-band offset dishes you can sometimes adapt Dish/DirecTv/Hughesnet/Direcway/WildBlue/Primestar/Channel Master/etc. az/el mounts.
My First Commandment of FTA: Never buy anything if I can make or scrounge it.