A friend of mine likes coffee a lot and has a Rocket espresso maker with this Clive Style 7 Portafilter that he wanted a good fit for: https://clivecoffee.com/products/clive-style-7-bottomless-portafilter . I custom-made him this tamping station out of ABS after a few try-fit pieces and adjustments in PLA. STEP file included. This is a quick remix based on @rotf101's design.
I hope that it can help someone else without having to spend all the extra effort I needed to get it right!
Printed the final version in ABS to resist deformation if the portafilter is still warm and for impact resistance.