There is a variety of short, fixed handled shovels that would work for you. My first was acquired when I had a VW beetle, in which space was at a premium. Dunno where it is now. Maybe 600/700 long with no T handle. Worked very well for latrine holes and light bog (no pun) removal. Short, fixed handled shovels are also very handy if a wheel needs to be changed.
Nowadays for those duties or as a "just in case" I carry something like this.
https://www.aussiedisposals.com.au/aust ... hovel.html Compact, functional, and nearly soldier proof. Not much help in wheel changing.
If I have room, or anticipate much need, I carry a long handled post hole shovel, which will reach well under a vehicle and is comfortable to use for other excavations. It fits inside, and across, the tail gate of the Hilux, but I think would be a pain in a conventional car.