ᐅ IKEA Rationell drawer by Hettich and from which system

I have several Rationell drawers here and would like to reduce their width. Now I’m wondering which Hettich system they come from. Does anyone happen to know? These are not Blum drawers. The front mounting and the side locking mechanism can be found in the Hettich range. However, I can’t find the other components like the drawer slides or the side panels.

I spoke with Hettich today, and they told me that while the rails and sides are very similar to those from Hettich, they were not manufactured by them. Are there any other manufacturers that could be considered?