IKEA carries 180x200.  Largest I've seen here....

I have 160x200, and I have found it to be big enough for myself and 2 girls.

Choose the girls a little more carefully and three will be no problem.

Thanks Andrew for your POV but I shudder to think how uncomfortable those girls were. I really hope these girls are your young daughters or else I might be worried at why you (seemingly mature in age) would have "girls" in your bed.

But really, a 200x200 bed would be perfect. I had one in America and its the only bed I can sleep in without being yelled at for kicking my boyfriend. That extra 20cm makes a BIG difference! :)

I guess I could say something about colloquial terms, but anyway, yeah, I agree with you, the bigger the better. And when it's a square you can sleep sideways too. Good luck.

You can easily find some, just google and / or visit some shops (they can create your dream bed if you just ask them) :

http://futon.ch/public/article/view/id/110160

http://www.makoura-futon.ch/pages/litsettatamis.htm

You can custom order a Tempurpedic bed in that size. IKEA actually sells bed platforms for that size but you will have to order and wait for them. 

I have 200x200x25cm tempurpedic mattress on an IKEA 2 piece pop up storage frame. 

This is an expensive option but you are going to spend 33% of your life with it for the next 15-20years. It's an investment. But the comfort and quality of a Tempurpedic mattress is extraordinary. 

www.tempur.ch