Found them. These are the ones I used, but look to be a lot more expensive now.
https://www.discountvantruck.com/rvs...powerbases.htm
But in the 10 years I’ve had them, not one single problem.
The biggest thing to making your own, is you can set the amount of legroom for the passenger. It’s dam cramped in any stock location, these allowed me to set it as OEM but in the rear most position, a lot more legroom. Something you can’t do with the manual sliders as their distance is less.