Do you keep Halav Yisrael?
Schmerling makes light spreadable triangle cheeses that go well on celery and that are 60 calories per serving.
They also make Swiss cheese singles that are ok; they’re in a green package, and around 45 calories per slice.
If you don’t keep Halav Yisrael, Smart Beat makes rather tasty and relatively inexpensive American cheese singles that are 25 calories a slice (OU-D). These are my preferred choice.
I find that it’s often better to eat less of the “real” thing. I’m of late a fan of cheeses made by the Cheese Guy (OU). Perhaps I’m a bit of a foodie or snob, but I’d rather have less of real cheese, such as Montaggio, Lo Spadone, or Danish Blue cheese, than larger servings of processed cheese foods.