Can anyone recommend a REALLY sturdy catflap?

[KateBC]

My parents picked up a cat from the shelter yesterday, who is lovely but enormous! he is going to have the run of the house, but at night they want to keep him in the utility room (which has access to outside when he's settled).

Last night was his first night, and within half an hour he had pushed through the locked catflap and pulled it off the door! Admittedly it has been there for about 20 years, so probably about time, but can anyone recommend a really strong one to keep him in his room at night? Don't want him in kitchen at night as they are getting cat number 2 from shelter in a couple of weeks, and last time two cats were left in kitchen overnight it resulted in a lot of broken crockery!

Tia

[Lizcat]

We have a Sureflap -microchip flap that even when the evil invader headbutted it at full pelt held firm.