I've had this Paddle Bag for about a year now. This South African product is available in the US from Ocean Paddle Sports for $100.
The bag has an appropriate-seeming amount of padding. The retailer claims it can handle two 2-piece paddles, but it only has one separator (which works well for one 2-piece paddle). I don't know how well it would work for two 2-piece paddles.
The bag has two cavernous clothing compartments which are designed for wet clothes. I was shocked how much clothing I could fit in there (i.e., it was a lot).
I really like that both sides of the bag have a large built-in warning label "FRAGILE -- GLASS". I spoke with world-class professional surfski racer Dawid Mocke (whose company markets this product) about it. He reports that he's been using it for a long time. I asked if he's ever had any paddle damage when checking the bag on an airline. He said that only once (out of many, many such flights) has there been any damage. Given how badly I understand many baggage handlers treat baggage, and how much air travel Mr. Mocke does, I think this is a good testimonial to the effectiveness of how well this bag protects its contents.
While I am happy with this product, I think that, if I had to do it over again, I would have gotten the $75 NRS Two-Piece Kayak Paddle Bag because it costs less and appears to have similar, if not superior, functionality. My major complaint about the NRS bag, in favor of the Mocke bag, is that the Mocke bag has those big "FRAGILE" warnings -- that hopefully would help somewhat to avoid hard handling by the airlines.
One paddler I know claims to be happy using a hard-sided gun case, though I haven't actually seen one being used in this way. I guess you could take your paddle to a gun store and just see which (if any) such gun cases fit. If you found one that would fit, I'd imagine that this would provide the ultimate in protection.