views vary....as ever....
purpose made stilt bags..pro jumps has 1 for sale.....or borrow mine. Mines actually bigger and I think better. Has more room for cloths AND cheap booze.
Any padded sports bag. Golf bag ( often has wheels wot helps) Hockey bag as examples
Cheap option, get big suitcase. Take springs off and put frame in case, if lucky springs will go in too. If unlucky just tape/tie springs to suitcase, you could wrap springs in bubble wrap or loads of newspaper if u want.
But realistically....wot could a baggage handler do to the stilts....that we ourselfs dont already do? think about it.
Im not sure the stilts really need much protection.
But do be aware of airlines weight limits and also size/dimensions limits....or you will get an unexpected surcharge at airport.