REI has a Timbuk2 Sonoma bag on sale. It looks similar to the Apidura. Timbuk2 stuff is bulletproof, but I'm sure heavier than the Apidura. Its also around $50.00 or so.
I have that seatbag. I quite like it for day trips gravel biking and put my pump, spare tube, gloves and jacket in there as well as snacks and phone. But it doesn't fold flat either.
