Yes they can easily be scaled to fit them. I have 73mm and 85mm holders. The smaller one is pretty universal for most store bought bottles and the bigger one is more for cups and glasses.
A collection of cup holders that slide between your couch cushions. Free to download https://makerworld.com/en/models/1318086-cup-holders-for-sofa-cushions#profileId-1353638
Yes any standard sized utility knife blades should fit. I tested a bunch of different brands from my local hardware store.
I have a 3D printer buyer's guide on my website that lists a few. I mostly use and would recommend any Bambu printer, there's a few that can suit any price range. Elegoo also make good printers too which won't break the bank
My two are pretty good with not eating things they shouldn't so I just made sure stringy bits were cleaned up. Googling says PVA/wood glue is safer for cats but I would check brands if they are non-toxic
STL files available on Thangs
I have the STL files on Thangs for 3D printing.
Also good for composting and making room in your recycling bin
