Vesa 100x100 to Vesa 400x400 adapter?

I am planning to get 3 of these mounts for my setup:

http://www.comx-computers.co.za/UNIM4255-UniMounts-Gas-Spring-Mount-Bracket-for-42-Buy-p-158447.php

However, they support Vesa 400x400 for 42"+ TVs... I have 3 24" Monitors with Vesa 100x100... So I need an adapter of some sort? Any ideas?

Thanks in advance!