Bed slatholder with size 57x11mm. I printed it with Polymax PLA and it works without problem. I've also included the source file (.slvs). This file can be loaded into the free and open source Solvespace, a 3dcad program. 

If the size of your slat differs but you don't want to redesign the source file (.slvs) of slatholder yourself ask me to design it and I will upload the stl here.