Some questions on bags

How many slots do the level 30 and 50 reward bags from the Slow And Steady challenge have?

On Ambershire, how much are the mats for a level 12 and 14 bag? Are 14 slot bags the largest ones that tailors can make in Turtle WOW?

Are there any relatively easily available, large bags (12+) out there that you can get from quests and events?