Animal carriers + Bags

We are looking for a suitable bag (actually 2) to transport our two cats intercontinentally in the cabin (due to relocation). Unfortunately the given dimensions (55x40x23) are very small for our 5 and 5.5 kg cats, especially with the height... Does anyone have experience with certain models and can recommend a specific product? We would also be grateful for your experience regarding Swiss; for example, whether the dimensions really need to be followed very strictly. Many thanks to all in advance.