Paint.NET :: Easy Way To Remove Random Single / Groups Noise Pixels?

I have pictures that have different objects over a canvas like/un uniform back ground.

I need to remove that background without any part of the objects them self.

I mange to get most of the background out using the magic wand , but i'm left with many random single/groups of noise pixels left in the picture since they were not captured with the magic wand.

most of the time i can remove those using the eraser or use the selection tools with different shapes around the pixels and press delete.

but those methods take lots of time, specially around a complex objects and as i'm getting near to them, i need to make my selections/eraser radius smaller and smaller.

I have tried to use a plugin called "Reduce Noise" that i found , but it does not work.

faster way how to remove this noise pixels without any part of the objects?

a plugin that "scans" the image/selected area and remove all pixels that are surrounded by transparency in it?

p.s I can't always select only the object/s itself/them self and just move it/them to a new picture.

p.s.2 maybe a plugin that the user can choose up to what size, a group of pixels, should be removed ?