Musty smell in vintage handbag

Put the bag in a sealed plastic crate with one or two Neutradol gel things inside. Check after a week and continue until resolved.
Worked for me with a heavily smoke infested vintage Mulberry bag.

Do you have one of those things some people put in their fridges to absorb smells? That might work. Otherwise a small amount of cat litter inside a little bag?

Bicarbonate of soda is good for removing smells , just sprinkle some in the bag and leave for as long as you can and it should help a lot.