You will not get one with the size of top platform you want Gill. I have looked everywhere. No matter which one you get you will have to put a larger platform on yourself and probably a couple of supports.
My home made one has a large platform on top supported with 3 shelf brackets. Mind you the larger 180cm one I posted the link too would be very easy to alter, just screw a larger platform on top of the existing one
The kitty city is a bit wobbly to have that high in a single tower, you would have to buy more and build it up like steps like mine, so I don't think it would be suitable. I had problems with it when I bought it, it kept coming apart but they sent me replacements and now is good. The poles weren't tight enough
Good hunting