Hey Pablo,
I live in Europe too. So the Variant Covers are Direct Market Editions, that means that you get them only in (online) Comic Stores. Amazon won't sell them.
It's hard to get them cheap and most of the time they are oop much faster than the standard editions. I only own one Omnibus with a Variant Cover, because
they are hard to get and I'm not willing to pay so much only to get a different dust jacket.
For example you can order them here, but I don't know if all of them offer international shipping.
www.archonia.com (I think located in Belgium), never bought there comics on my own e. g. Uncanny X-Men Volume 3 Variant ~90 Euro plus shipping
www.comicexpress.de (German Comic shop), SRP in Dollar = price in Euro
www.comic-heaven.de (German Comic shop), poor product range, but price is ok (e. g. I think they had the FF4 Omnibus by Byrne Variant for around 60-70 Euro few months ago)
www.forbiddenplanet.co.uk (British Comic shop), good product range, price is ok, pre-order the Omnibus with variant covers!