its a custom staircase. we ended up designing and fabricating the stairs, because it was more cost effective than anything we could find off the shelf.

You definitely won't find one premanufactured and ready to install as all of the design variables are very unlikely to be found on a prefab unit.
The floor to floor height is the main variable used in creating stairs like these and this dimension can be any number. Then you have the radius needed and the width of the landing. Also, you would need to establish the entry point on the bottom step in relation to the exit point on the top.
The short answer is- This would most likely need to be custom made.