That's good ol' misterdotcom. Famous in the States for their cruise control systems and makers of pedal mappers long before SmartMadness got into the game.
They cost more because of their custom fabrication and European transport authority certifications...certs that are meaningless on this side of the world.
These hitches are actually significantly weaker than the one you can buy from Curt in America and are less versatile. I think you'll still be better off buying a 451 hitch and having it fabbed to fit onto a 453.
Darn, I guess I should have taken the smart car universe one I have on my original Max and kept it. According to that ebay write up that type of hitch (replacing the crash bar with a hitch bar) fits both the 451 and 453 series. The smart car Universe one was made very similar. Here are the pics from 08 when I put it on Max.