I think originally there were two holes drilled for each mounting bolt( not positive, it's been awhile since I looked). If you get it cheap enough you could weld a piece of plate and redrill the holes. Piece of cake.
Take the one from Terry. Welding on the steel crossmember will patch the holes, but it will weaken the steel. You'll have some vibrations in the drive-line afterwards. (Please don't ask me why I know this!)
Hmmmm. "Fair price" ... I don't really know. I replaced the one in my GTO for $30 from a local junk yard. Luckilly, the GTO cross member is the same regardless of the trans installed.