Simple electrical question

[UnworthyBean]

I've got two or three Ikea lights that all have their own plug and switch. If I wanted to shove them all on the same plug and switch, whats the easiest way to do it?

Can either use the existing switch and shove a junction box after it or replace pretty much the whole lot with some other solution?

 

[UnworthyBean]

Should've mentioned I did consider that. It's going down the back of a bookcase and ideally not enough room to shove the extension in there.

My logic was if I could get it done like this, it wouldn't add bulk and just the switch could be mounted in an easy to access place.