Choosing a Polaroid camera
Since the discontinuation of all roll and pack film, and Polaroid resurrecting integral film, your camera choices have shifted to Polaroid's newer cameras. Foldable SX-70 cameras are very fine cameras, but require a flash source indoors. 600 series cameras are the most common cameras, and they usually have built in flashes, and a wider variety of instant film. Note that Spectra film is no longer produced so Spectra cameras aren't viable anymore.
Now, technically at this time (2021), you may be able to still order 100 series pack film from One Instant. And if you're willing to pay $15/picture or try finding expired pack film at $70+ per pack, then you must be serious about use pack film. In that case, you would also need a serious camera. I would think anything less than a model 180 or 195 would be wasting the film. Better yet would be a medium format camera such as the Polaroid 600SE with a Polaroid back, which would give you options with your lens choice.
If you are intent on taking instant photos, consider Fuji Instax cameras. Personally, I don't like their mini format, but they do make a square format similar to Polaroid 600 and a wide format similar to Spectra. Fuji still makes film for this camera as of 2021 at a reasonable cost.
Another option is to convert an older roll or pack film camera to use another type of film. The three main options are:
photographic paper negatives: this normally involves removing the roller assembly and building a film holder with dark slide. Exposures will be much longer (paper has a film ISO of 6), and you will only be able to do contact prints, but you can still use the camera. You can use single paper negatives without modifying the camera if you load them into an old film cartridge and store them in a black bag, then load/unload them in a dark camera bag on the field. Because of the long exposures, you will need a camera with a tripod socket and a cable release, as well as a light meter. The paper negative concept is explained in this video. The process of using paper negatives is shown here.
120 roll film: The easiest camera type to convert to this format are roll film cameras. This requires removing the roller assembly and creating a spindle and knob to advance the film. Using this type of film means your Polaroid will be a traditional film camera.
Instax film: Both roll and pack film cameras can be converted to use Instax wide film. This involves cutting the lens assembly off of an Instax wide camera, wiring the motor directly to the shutter switch, and modifying a cam to advance the exposed film out of the back. Then, a Polaroid pack or roll film camera will need to be modified by removing the back and cutting away the side and bottom, then mounting the back to the camera with some foam inserts to prevent light leaks. A mash up video of this process can be viewed here Details on preparing the Instax camera as a back can be viewed here. Because the film plane is moved back, a modification to the focusing scissors is necessary on pack film cameras. The 110 series roll film cameras apparently can adjust infinity, so these cameras may be more suitable for this conversion. A pack film camera used for this conversion should have ISO settings for 300 in order for the automatic exposure system to work.