In most cases integrated appliances have fascia panels to allow them to fit into a range of voids.
What is the dimension of the void the new microwave needs to fit in?
Your best bet is to use comparison sites such as the one here to chose appliances which meet certain dimensions, as you dont want to find a microwave the same size you just want one to fit the same void.
Failing that its a case of adjusting the cupboard, height, as most microwaves are around 56cm, so its just finding something to accommodate the depth and height.
Please let me know if you have any follow up questions
I will opt out as I am not your personal shopper.