All thanks to my prodding the manufacturer for two years to come up with a vegan D3 formula - you can thank me later
But, in all seriousness, I have been in contact with them (they developed the original V-Pure product and are the makers of Opti3 DHA/EPA) for some time, and put them to the challenge of coming up with a vegan D3, which they certainly did create. It should be available here in the end of August, I've got a big pre-order set for it the first moment we can get it shipped in.
There are actually some new mushroom-derived vegan D3 supplements that just came out as well (actually vegan, not the Garden of Life "we call it vegan even though it isn't" stuff), should have those in stock in the next week or two as well. Strange when those times come around where something that has never existed before comes out in multiple versions at the same time!