Heavy Tailored Legendary Bag  

 

Unexpanded Tailored Legendary Bag (1) Crafted

Inverse Arcane Solution (1) Storebought

Trivial is 15.

NOTE: If you have the Unexpanded bag in one of your bags and the Tradeskill Window shows it is green and you hit the Combine button, it will balk and say:

Sorry, but you don't have everything you need for this recipe in your general inventory.
You are missing a Unexpanded Tailored Legendary Bag.

Just hit the Experiment button and manually place both items in the tailoring container and hit the Combine button.