Note: There is no such thing as an H-class hazardous dust wet vacuum.
That is because a wet vacuum does not pick up dust. It picks up slurry or wet hazardous materials.
What you may get is a vacuum which is part wet non H-class and part dry H-class. The fact the materials are wet means they don’t pose a risk of inhalation. However the waste still needs to be disposed of as contaminated.
To add a filtration system to the vacuum you would have to add components to the unit.