Opening portlight in perspex window

[Sea Change]

In an effort to improve ventilation, I'd like to add an opening portlight in our large perspex saloon windows.
Is there any particular type of hatch I should be looking for? The perspex is about 5mm thick.
The window is only 23cm high and I will need to leave enough perspex around the opening for strength, so I suppose the hatch will need a fairly neat surround in order to leave a meaningful opening.

 

[Tranona]

On my Bavaria I had these set into the acrylic windows, one over the cooker and one in the loo. Worked well, and on my long list plans to fit them on my GH.
lewmar.com/content/standard-portlight-opening?v=24314

 

[Sea Change]

On my Bavaria I had these set into the acrylic windows, one over the cooker and one in the loo. Worked well, and on my long list plans to fit them on my GH.
lewmar.com/content/standard-portlight-opening?v=24314

That looks like the right kind of thing, thanks.

 

[lustyd]

Might be worth a watch, they just did exactly this job