Uh oh, new competition!
You can see the tool I use
here.
I buy my snap edge from Unilock, they'll discount quantities.
What I've done is cut 2x6 lumber to different lengths to screed with using the 3/4" conduit I posted earlier. I've looked at the tools available from Pave Tech for screeding and while they'd be nice to have, they're a bit pricey.