Hi. This is my first question to this forum.
My house was built in the 60s and has 2 plaster ceiling vents - one in the bathroom and the other in the kitchen. The bathroom vent in particular let's in the horrible paper mulched insulation dust as well as ****. I'm looking for ways to cover them up without them looking super ugly. The ceiling spaces are difficult to get into to cover them from within the roof cavity, so I don't want to do that. I've thought of a painted board, plasterboard, plastic type board, but don't know what would be best. I'll attach a photo of the kitchen vent, but they're both the same.

Thanks