I wanted to buy a regular shaker incubator for expression. Does it have to be an incubator shaker with filter? Could you please discuss your current setup?
You can get cell culture flasks that have filters built into the caps (eg. Corning). You can also place the plates in a sealed box that has a filter inserted and sealed into the lid. Overall try and keep the work area as clean as you can and give the bottle a good spray with disinfectant before handling in a laminar flow hood.