Pipefitters use them, I have found them useful for all sorts of
spreading and aligning. Anyone know where to find such a thing?

yea, I've seen and used them also. I got a whole bunch of 24' 2x6 nailed
together into a post a while back. I used wedges to drive to drive them
apart . Made quick work out of a tuff job.

I just built my own. That's why I own a milling machine.

Karl