Hi Jonathan;
When I was first getting into the industry, I had a romantic vision of acquiring a large stone melangeur as well, (saw one at Scharffenberger's factory). They are very veryhard to find, but I've heard rumblings that some Italian companies have considered starting to manufacture them again to address the growing artisan market demand.
There are however other more efficient (and lighter) solutions. I can't share everything with you, but I hope this post will help save you time looking for something that you may not find, and allow you to be more productivefocusing on a better solution.
Cheers
Brad