I've been looking for an ideal case for both my Cannondale Quick Carbon 2 (ended up with a Thule from a Facebook sale) and my folding bike - a Tern Eclipse p20. I already have a rolling case from B&W for my full size Change Bikes folding rugged hybrid - and searched high and low for something big enough for the Tern - eventually settling on an Aophire 26 inch folding bike bag. It's decent and relatively low cost. Fits perfectly and with padding should be a no brainer for aircraft travel and never incur shipping unless I get a mean desk person.
https://www.amazon.com/Aophire-Foldi..._ap_asin_image
BUT... if like me you've looked for something tougher and big enough for a large folding bike or a disassembled regular bike - consider Car Cargo Roof Bags! I found several that are nearly perfect for the Tern's dimensions and still reasonably cheap. I had already bought the Aophire, but was shocked at how many fit my exact requirements at a reaosnable price.
This one for example could easily hold my full size and folding bikes and would simply need to be padded appropriately inside. If it had rolling wheels it would be ideal, and it might be possible to mcguyver some skate wheels onto it. I'll update if I do it.
https://www.amazon.com/MIDABAO-Water...%2C304&sr=1-39