After much internet digging, came across an article from H&R that does make springs for the GLB35, only in Europe.

https://www.h-r.com/2025/03/03/suv-performance-pur-hr-tieferlegungsfedern-fuer-den-mercedes-benz-glb-35-amg/

Have reached out to H&R USA to confirm if they can ship the same product number to the states. Hoping they have some good news.

I had the H&R springs installed in May, and I've been loving them. The ride got a bit rougher (comfort is now similar to sport setting previously), but the car looks much better and getting in has become much easier.

Boy! Looks great! This is how the sport mode should be sitting. How's the speed humps? Any issues?

I still have the springs sitting in the garage, and haven't installed them yet. 😂 Feeling motivated to get them and the wheel spacers put on now. 👍🏻

With such a minimal lowering (15-20mm) the ground clearance is still pretty good (higher than most factory hatchbacks or sedans). Speed bumps are not an issue at all.
That said I'm used to driving VERY low cars, so I angle every single driveway / bump. Compared to those my GLB is very high off the ground, so I can judge pretty well where it would bottom out.

As for spacers, I'm running 20mm all round. 25mm would be perfect for flush fitment without lowering. However after lowering camber increased a bit, so you need about 30mm (~ET20 with 8.5" wide wheels) for perfectly flush fitment.
Next season I will be getting wider 9" or 9.5" x 21 wheels with ET30 or ET36 respectively to make sure it looks as good as possible.