I purchased a 9 piece Reamer set (2-10mm) on aliexpress for cleaning out holes in my 3D prints. They came in a bag, so I designed a compact case to keep them together and protect their cutting edges.
It worked well for me in PETG, bumped up the infill to about 50%. No support needed. It's quite a slender part, so depending on your bed adhesion, a brim might be a good precaution. The lid is a snap fit, it works well on my printer, you might have to sand it a bit to get a consistent fit.
I can provide the Fusion 360 file if you want to modify.
The author marked this model as their own original creation.