Your best option is Nikon FM2 camera with the standard 50mm lens. You'll have to search among used cameras for this model. Try to find one that has minimal telltale signs of use.
Another good option is Pentax K1000 with the standard lens.
Apart from the above two classics, you can buy a Nikon FM10 (a cosina made camera) and exchange the kit lens for a standard 50mm f/1.8 lens.