I think there are a few out there, but all expensive – Tacx NEO Bike for example. The ‘easy’ way is simply to buy some power meter pedals and attach them to the static bike of your dreams. At which point, given the cost of power meters, it might make more sense to buy a Kickr or similar and a cheapo bike – you don’t need brakes or a rear wheel, just a sort of shell bike, which is my project for the next week or so, though tbf, I already have most of the bits I need.
Edit: list of compatible stationary bikes on here:
https://zwift.com/hardware#ready
Fwiw, if you can tell Zwift what power you’re making, either with a power meter or by the bike itself, Zwift’ll know how fast you should be going. But unless the thing is controllable, you won’t feel the gradient changes, which is a big part of what makes it immersive.