I use 5.11 RUSH 24 to carry my Leshiy 350mm. It works great for me ... One of quality tactical backpack for hunting, hiking & EDC that you can trust ...
Or you can go with GORUCK if you want a top quality backpack.
Ogio Tech Vault. $35 at Costco. It's anything but tactical, made for laptops and other tech gear. 19" tall and fully padded all around and between all compartments. Two full sized laptop compartments with one that zips fully open and a main compartment that holds a guppy tank perfectly. Lots of small zippered compartments and one that's hard shelled. It's perfect for a Leshiy in any configuration. Like I said it's not "tactical" but then again, I like to blend in. It does come in black if that helps....?
If you prefer high quality then look into Eberlstock tactical line of backpacks. The Cherry bomb pack is 23.5 inches long and has several pockets for extra gear. They aren't cheap but are awesome packs. The secret weapons pack is a larger size and measures 31 inches if you have longer bullpups.