I, uh, already tried. I still have empty baskets, despite a forum thread a week ago.
Sadly, I’m pretty sure I’ll have to dig it up myself in the end, because I can definitely not afford 1-2c per rock, as I rarely get over 10k coin total.
Honestly, I was hoping to rely on people of Dzassak who’s been building as well, and just got the rock as a byproduct of excavation, but sadly I don’t think it’ll be feasible. I just need way too much rock, as I’m not using any stones for the moment. 
I’ll admit, too, I’m surprised at just how fast this thread grew overnight.
Edit: Found my old thread.