Do you have a store in Belgium that sells these types of monitors at all? Even Newegg.com, which has very reasonable prices and frequently offers free shipping, won't even ship internationally. I'm sure other people could think of a website that would ship to you, but that would likely take a significant chunk out of your budget, which already limits your options. Newegg only has two 120Hz monitors that are within your price range at all.
One from Acer ($290 U.S.):http://www.newegg.com/Product/Product.aspx?Item=N82E16824009222
One from Asus ($360 U.S.):http://www.newegg.com/Product/Product.aspx?Item=N82E16824236092
And one from BenQ, who I have previously never heard of personally ($390 U.S.):http://www.newegg.com/Product/Product.aspx?Item=N82E16824014270
If there's a supplier of one of those somewhere near to you those would all be within your price range assuming the prices haven't been inflated too badly (which probably they are). I am personally holding off on a 3D monitor until the prices drop a little bit and the market has more to offer, but that's just me.
I can also suggest going to Asus' website: http://be.asus.com/
They can probably give you at least some information on where you can find a dealer nearby.
So can Acer's website probably:http://www.acer.com/worldwide/selection.html
And then maybe BenQ too I guess?:http://www.benq.com/
I'm certainly no expert on the matter and I can almost guarantee there are other monitors out there you could potentially afford, but I am unaware of them or how good they are, sorry I couldn't be more helpful