DaseinWomen Barrel Handbags Purses Fashion Satchel Bags Top Handle Shoulder Bags Vegan Leather Work Bag

Q: Will this fit an a5 planner?

The size approx. 12"W x 8.5"H x 6.3" D, It will be suitable for an A5 planner in my opinion.

Q: Are the handles large enough for it to be worn on the shoulders?

The handle interior circumference measures about 14 inches, so if your upper arm measures less than this, you could probably wear it on your shoulders, but the bag is quite bulky and might be uncomfortable. The side measures 4.5 inches at the top, 6.5 inches at the bottom, and 8.5 inches long.