Slim Kärcher to osVAC Adapter. It uses my osVAC leak tight design, so you can insert a 37x32x2.5mm O-ring. If you don't have an O-ring at hand just leave it out, it will work as a regular osVAC coupling then. And the Kärcher vacuums have sufficient power so the tiny bit of leakage won't hurt.

The fit is quite tight, you might have to use a bit of sandpaper to achieve a smooth fit towards the vacuum.

Update 2026: The button of the original version breaks easily along the layer lines. Therefore I added a modified version where the button is printed separately and oriented on the side so it is more rigid. To assemble body and button, insert a piece of filament as shown in the foto and cut it so that only a small piece remains outside. This little piece can be heated with the heat gun or lighter and then press it down with a flat head screw driver so they act as a rivet. I had to clean up the holes with a 1.5mm drill.