One
here which you've probably already found...
We always noticed these screens when holidaying in France - great for keeping mozzies out but the lightweight ones aren't any good for cats. We had a visiting cat one year who would come and lean on the screen to let himself in!! Presumably he'd learnt to do this over the years but the mesh simply popped out so he was triumphant when he arrived on our bed ...every night at 3am and usually with a dead furry gift :)
I wonder if you could talk to a handy carpenter or DIY man to make you something. If you have standard sized windows you could probably get him to make you a pop in frame which could then be moved between windows. Alternatively have a chat with a local window company to see if they have any recommendations or can help you.
Whilst at the aforementioned holiday home, and after 5 days of nuisance visits from this very noisy (and flea ridden) tom cat, my husband made a screen from some wood and chicken wire (actually smaller holes than chicken wire but I'm sure you'd get something like it here too). Not very glamourous but very effective and cheap too, just be sure it's strong enough to withstand a climbing cat and well secured in the window aperture. This might be a good temporary option whilst you do some more research