Down in the town I go to for supplies and such, there is a second hand store. I always stop by here to see if the owner has or knows of any classic gaming stuff, esp. CV and the like- he watches for it.
Today, when I went in, there was someone else there. He immediately pointed me out, asking if I was looking for "Atari" stuff. He meant 2600, so I said no, but we soon spoke of other games- he is still a Vectrex fan, and he was amazed when I told him that NEW games were made for consoles like the CV and Vectrex. In fact, I had to specify NEW, not "old games recently purchased."
After I told him about this website (he is the second; another may have been here already), he swore that he once had TEMPEST on cartridge for the CV. I asked him the obvious questions: did he mean the 2600 or 5200, a computer game called Tubeway, etc.- but no, he was adamant about it; a bootleg version of Tempest for the CV.
(Some years ago, there was another CV fan who lived nearby who said that a relative of his, who worked at Coleco (this place isn't that far from Amsterdam, NY), had loaned him a version of CV Centipede that played like the Atarisoft version, but was given much better graphics.)
That person who told me about Tempest was clearly not goofing around, and he was no doofus- he knows his classic consoles. Therefore, it's entirely possible that this cartridge, like the improved Centipede, does in fact exist.
If ever either finds either, I will update this post.