It's a supply and demand problem. Producers will make more chastity videos when people begin asking for more.
A secondary problem, though, is what constitutes a chastity video. Is it somebody simply wearing a device? Wearing a device while having sex? Wearing a device while washing dishes?
A few years ago I ran across a grainy B&W clip of a man on his back being taken by a woman with a strap-on. Though poor quality, you could make out that he was wearing a CB3000. It was only 15 or 20 seconds, though.