Cat-proofing Velux windows?

[Toaster Pilot]

We have two cats, one 11 months old and one 6 months old, both indoor. They seem to have taken to trying to get out of the Velux windows in the upstairs of the house, resulting in both of them recently having falls off the roof (thankfully seem to be fine - idiots!)

Are there any products out there that would let me leave the windows open but have some kind of screen over them to prevent them being a cat escape route or am I stuck with them closed boiling to death in this heat?

[Toaster Pilot]

8bit said:

Do your Velux windows not have snibs that push into holes around the wood trim to hold them just open a little bit? Ours does, I only realised this recently. Before I realised that I was planning on getting one of those little rubber door stoppers and fixing it to the side of the wood trim such that the window would only come so far open.

I don't think they do (they're ~20 years old and pretty buggered) but I'll check