Okay--- before anyone snorts coffee or soda into their sinuses---
I have had success with, uhm... ladies pantiliners.

The liners that has an "fresh odor activator" (e.g. Carefree Acti-Fresh).
The idea just came to me one day, I removed the paper strips from two pantiliners and pressed the adhesive sides together for a double sided "wing"

and placed them all over the bag, in pockets, in compartments, outside the bag in its dustbag.
I'm serious, after a week, I didn't smell anything. A very inexpensive and tidy option.