Yes, but they may be called dual Cal rather than split, and not all brands make them. Beautyrest and Tempur-pedic have a good selection. More on reddit.com

Bought a split Cali king this summer with a L&P adjustable base. Highly recommended for sleeping. Can't be beat. Terrible for everything other than sleeping. Tile floors. I failed to fully appreciate an adjustable split king is literally two separate beds pushed up against each other and nothing anchors the two together. Mind the gap. Def a no-go if you're a frequent spooner. You might have better luck on carpet or a traditional frame. Even on a traditional frame, though, the gap between the two mattresses won't meet perfectly and seal. It will always be there like the cushions on a couch. Good luck! More on reddit.com

I love my split king. I sleep better and we keep a few inch gap on our adjustable frames. I ruin mattresses and she doesn't.. I bought a 4.6k intellibed midnight and she is still on last year's purple 4 and my old one is in the trash. For sex it kinda sucks but I'd rather sleep perfectly then worry about that. My wife is a crazy sleeper. And now I sleep better without disturbance. More on reddit.com

Buying two twin xls with the same firmness without bases is utterly nonsensical. Sorry. More on reddit.com