It is disappointing that the SVR program attracted such strong reaction. I had the idea for an inexpensive transfer reference around 2003 and bought the FLUKE 732B back then to try make it work. I learned later that there had been similar efforts with LM399 over the years, but as far as I know, no low cost boards for hobbyists and engineers.
My idea was a small board similar to the "International Crystal" small board kits from the 70's that old timers might recall.
There have been any number of similar approaches from boards to small boxes, at least from a couple of years after I began to sell AD587 based references on eBay.
One of the most difficult aspects of this sort of product is the wide variety of what users are looking for. For example, I got several complaints from Simpson 260 owners that turning the trim had no effect on the output voltage. Others, as discussed at great length here wanted it to be a long term stable voltage standard. Ironically, many of them have done quite well over years, but my post is not to debate that point.
I wish you all great luck in your own designs. I see new design ideas all the time. It is very likely that a great long term stable reference may emerge. Possibly for under $100. Great fun!