@yeetus
flyeralarm is pretty good for standard shapes (square, circle, DIN, some fixed rectangles). pick the thicker paper (e.g. 90 µm or more) for better results.
https://www.flyeralarm.com/de/p/outdoor-aufkleber-4245640.html

wir-machen-druck sometimes has more options but their print quality has been hit or miss

@yeetus @mxl Custom shapes like that are typically called "(unregelmäßige) Stanzung" by German shops, should be supported by most big places (sometimes only for a hefty surcharge though).

I've made good experiences with stickma.de fwiw.