I had a hard topped carrier for several years until a tree fell on the shed it was stored in and smushed it.
I bought a soft one at the Samsonite outlet for around $50. It turned out to be an excellent solution for us.
When we flew to Denver a couple of years ago, we took the carrier in the box inside a suitcase. The box is maybe 16" x 12" x 4". We went to the rental car company, selected a van with a roof rack, and installed the carrier on top. Lots of space for all our luggage when travelling from place to place. When we landed in a resort for a few days, we just took it off. When we finished our trip, we piled luggage in laps on the trip to the airport because we wanted to wash the carrier (think bugs .... so bad that we even washed the rental van once) and pack it up the day before. Back into the box and suitcase it went.
My husband tugged too hard on one of the straps and broke one of the latches. (Plenty safe with the others. Didn't miss the one.) When we got home, I went back to the store with it to try to buy a new buckle. They insisted on giving me a whole new carrier.
The box got put away with our luggage and we use it anytime we need overflow space. My husband and son have the installation down to about ten minutes.
We've been through many rainstorms with never a leak.
I haven't tried it, but supposedly it can be used even without a roof rack.
Sheila