After a few weeks of driving for driving for rideshare services I learned (the hard way) that you really need to have a barf bag at the ready, because you never know when you'll need one.
I ended up purchasing a dozen Dynarex 4707 emesis bags, which include a ring with mounting notches. This holder allows me to keep one mounted in my car in a location that is out of sight, but can be accessed quickly.
Optional: Sand down the attachment nubs
Depending on how you'll be mounting the holder, you might want to sand down the attachment nubs a bit to make the bag release more easily.
Mount using M3 screws and bolts
You can find them at any hardware store. Washers are also probably a good idea.
In my case, I attached the holder inside the lid of my car's center console. This required partially disassembling the console and drilling holes using the holder as a template.