One great option for the money is the Rockr Pod Lite at $150 right now.
I have used one for a decent amount of time and it is great bang for buck. It comes with inflatables that are adjustable, but I ditched them entirely and relied on the rib curve for centering. It is loose in the middle and naturally increases leveling force the further the rocker & bike lean.
Ultimately, it’s slightly stiffer at the 5-7* angle than I personally like, but I am a very edge case user. I think the default curve with no inflatables is likely close to what may work well for you. Check out my pics and review here for more info. I am happy to dive deeper if you have more questions too.
The other common option in that price point is the LifeLine rocker from Wiggle / CRC. Same price from each, but shipping can vary, so check both.
Take a look at both and let me know any more questions you may have.