I buy all my thicker card on ebay, my local office supply shops have different gsm rated cards that are all weird thicknesses like 0.67mm etc.
Then, like Rick suggested, I laminate to get the desired thicknesses over 1mm. Spray adhesive and a good flat weight, leave it overnight or longer.
Although, since you're in Europe, maybe check out
GPM I'm always seeing 1mm, 0.5mm etc card on their site but the postage cost to Australia rules that out for me.