While he doesn't have any in stock right now, David from Diamonds by Lauren specializes in fancy colored diamonds, loves radiant cuts, and has been selling lab stones for a while. I'm not an expert, but I would go straight to him in your position. We'll see what the experts say.
Here's a link of the current yellow lab stones he has, but he should be able to get more on request. https://www.diamondsbylauren.com/in...min=&price-max=&cat_id=310&ring_types=&page=1
I checked all those website and loosegrowndiamond. It has the lowest price. Does it mean their stones quality are lower than others?