Good news: I got that thing to work. The belt that holds the bags has a snapping type lock (like you have on metal transport boxes) with an integrated spring to give the belt tension. That spring was - to say the least - a bit too hard for the purpose. It just didn't stretch one bit while the lever already started to bend. I did lengthen the spring by about 5mm (almost tipping over my workbench in the process) and now it fits, nice and snug.
Bad news: the hose that it comes with is... stiff. Almost qualifies as a limp pipe. And the connection piece that is supposed to hold it on the machine (dangling below) is very lose. That means I have to fix that and build a "distribution box" kind of thing to get the hose diameter down to the size(s) I need and open/close them without having to plug in the hose to a different machine every time I do something. Gonna be a fun little "first project" in a few weeks.