Ofc, any time.
Not sure what you mean by "reputable sellers are unable to guarantee what they're selling", buying from people like Kevin at tuic, Dave at COTA or Ken Davis will provide you with true red devils. Labiatus is endemic to two lakes, and shared said lakes with various other amphilophus. Namely citrinellum type species. I say citrinellum type species because while actual citrinellum occurs alongside "labiatus" in lake Nicaragua, the Managua "midas" were recently found to be genetically distinct, and the name "amphilophus managuensis" is probably going to start popping up soon. This is besides the point though.
Unlike the midevils of Florida, which are likely only hybrids because they are descended from a time when people didn't care about locality or purity, closely related fish, especially amphilophus, seem to do a good job of not frequently crossing enough for it to become a problem for collectors. The "science" behind that being the fact that they fill different niches and don't usually interact enough to run into eachother and reproduce.
I believe there are only one or two true labiatus locales in the hobby right now, the weird "yaxha" ones, which I believe are actually from lake Managua, and the Isla zapatera ones, which are from lake Nicaragua. The sources I mentioned before all carry the zapateras. They seem to be the locale that's popular right now, I've even seen them pop up at wetspot. At the very least those are what people look for in red devils, and all those sources actively work to keep them from losing their big lips to captive breeding.