Retro renovation might have a resource. Here's a blog post that might lead to your answer... https://retrorenovation.com/2017/11/27/10-styles-mosaic-slate-flooring-including-random-multi-color-great-source/

I adore that style of floor! I have it in my entryway and I'd love to have it in the kitchen too. I suspect it will cost a fortune, because you never see it anymore. I know the brand Tarkett made cracked slate vinyl flooring at one point, you may want to call them. I can't find anything on their website but here's proof it exists: https://www.onlinecarpets.co.uk/broken-dark-slate-random-tile-texstar-vinyl-flooring.html 

I know this is an old post, but did you find a source for the tile? After contacting Vermont Slate Depot, they said their regular source for the "Crazy Pattern" (What it is called) just went out of business. Would love some help if possible! THANKS!!

Try "Vermont Structural Slate" (not the same company as the one you mentioned) We have purchased from them over the years and they have been very accommodating to our design and stone needs. You should have the sq footage and thickness needs available to discuss with them. I saw a black in the slate section, in the unfading line... and another that was a rougher texture. You can see in their "projects" section that they do the "crazy pattern" cut stones, so I hope they can help you.