Let user choose posts per page?

I searched a lot and I can’t believe I couldn’t find a solution for this.

I want the user to choose amount of posts per page through a dropbox or so (5, 10, 20 etc). Is there any plugin or way to do this easily? There is only one plugin that seems to have this solution that I found (DB posts per page) but it doesn’t seem to work..

I would appreciate some help!