Count your blessings
I bought a great leather wallet in Vietnam a long time ago. Beautiful wallet, loved it, but every time I worked up a sweat I smelled like I had just peed my pants. Couldn't figure it out. One day, after overcoming a hormonal perspective on my lady friend, I asked her if she noticed the smell. She says, "Sure, it's your wallet." Then she explained that it was tanned with elephant urine and whenever it got a little moist, it also got very fragrant. As for cover-up scents, a smell is a smell, better off without one. You know that if you smell it, it is smelly. I think the baking soda will work. That is why it is used so frequently in refrigerators. That coffee grounds idea sounded plausible, as well.