Good luck with that and with the flight! It is always best if you can have someone bring it over for you. The Sturdi Bag comes in different sizes, but the Large size was the only one that fit the sizes of the airlines I checked (Iberia, mostly). However it has a flexible top so maybe even if you buy the XL, it can still be accepted.
When we made our reservation for a pet passage, the lady from the call center asked for the size of the carrier. Of course she didn't mean "how much you can compress it".
The Sturdi was quite expensive in Europe, but I hadn't so many choices as there are in the US. The sherpa is cheaper, for example, but I don't know a lot about it. I just saw it is very popular on Amazon US.