Even though 55 produced both a neg and a print, you generally had to choose between producing a good print, or a good negative.
For compactness there are ready-loads from Fuji which is standard film in a sheath similar to the Polaroid's. Kodak made these also, but they are dropping them. These are used in a special single-sided holder, and can be used in a Polaroid 545 holder, so I understand.
There are also Grafmatic holders which allow you to have 6 sheets in one holder. Grafmatics can be tempermental, but are great for reducing the volume of stuff you need to cart around.