GEEeehhh...! Probably steel alloys also they are rated by the weigth need to support the heigth - wide - base plate dimensions and screws distances and all of that but geeeeh... I really don't know what to tell Ya' but I guess you can take a quick look at one of the biggiest like Mc Master or Grainger if I'm rigth.. Just check it out thruw the Net Surfing around the hood. Have a good hunting then now...
Buddy I did forgot to mentioned another good one to look for are northerntool.com if I'm rigth these guys carrie a lot of nice stuff there as well check it out later then. Allset easy does now. One day at the time.