This is a remix/combination of the two holders from @Scrappy79. I needed a couple more slots, but didn't want two separate holders.
I imported into Fusion, did a planar cut on the “large” file to remove three of the slots, merged the small with the now-cut large, cleaned up the fillets (that were now in the middle), removed a keyhole, and added a rib.
I'll add a real picture after I print it…
The author remixed this model.
Took the two “V1” files, removed 3 of the holes from the large one, combined it with the small holder. Removed a now extraneous keyhole mount slot and added another support rib.