Brewferm kits are the closest you'll get but their yeast isn't much good and Belgian beer is all about the yeast. Diabolo will be the closest to a Duvel but with the kit yeast it lacks the spiciness. You'll not get anywhere near an Orval with a kit as it has all sorts of different funky yeast in it.
You can quite easily grow Duvel yeast from the dregs of a few bottles if you've got a container you can use to make a starter in and some DME. I'm about to try putting Westmalle yeast in an abdij kit I had kicking around but think it would be good to try the Duvel yeast in Diabolo if you're thinking of doing it anyway.
There are loads of good guides around to show how to do this but drop me a PM if you want me to explain it.