Best 3G/4G worldwide compatibility ? (tablet)

[colinthehatchet]

Hello,
I'm looking after a tablet with the best 4G wolrdwide compatibility.
Because i travel a lot and in each countries I visit I buy a local 3G/4G sim card and it give me access to data network ways cheaper than roaming.

So I want a 8" tablet with a maximum 3G/4G usable bands.
I know that Sony Xperia Z4 meets this specs but it's too large and too expansive.

I saw the colorfly G808 4G which seems ok.
But is anyone know an other one ?

Thanks.