Yes this is getting surprisingly difficult. The old Fractal Design Node 202 is about 10l for 80$ and has a flat pizza layout but I would prefer a sandwich layout instead.
I have found this thread with a lot of recommendations but most of them are boutique 200-300$ cases or obscure single person manufacturers.
https://www.reddit.com/r/sffpc/comments/fe2rp0/sub_10l_itx_cases_full_length_gpu_support/
Example: Sliger SM550 (220$) or Dan A4 (215$)