Backpack to go along with carry-on suitcase

I’m sure you will get a bunch of suggestions that fit what you’re looking for, so here’s one to start off.

https://www.bagsmart.com/products/blast-travel-backpack?variant=41122671820882

I bought this for my son in the basic 28l size and he thinks it’s the best travel pack he’s had. It stores so much and with the clamshell design, allows for easy access to everything. I bought it about two years ago in black before they extended their versions. It’s a great pack.

Look for a trolley strap to ride on the rolling suitcases. Is this a supplemental pack, an overhead bin pack, or an underseat bag? For underseat bag, stay with 27 liters or less. Look at Osprey tote backpack or similar. Look at budget airline bags like Wandf or ecohub on Amazon. I would go with a few simple pockets and larger internal volume. Do you need an organizer inside for pens, key clip, etc.? We need more info. here.

Take a look at REI. Their website shows alot of different styles and sizes of travel and day backpacks. Many have trolley sleeves. A brand that is frequently recommended here, including me, that I think meets your criteria is Cotopaxi.

I've shared my go-to previously:
https://portlandgear.com/products/cascade-backpack-compact
It is not cheap, but is really well made. It has a trolley strap and creates the brick function you want- it doesn't stick out past the edges of my wheeled (July) carryon.
I carry it over one shoulder usually if not using the trolley sleeve.
It has a unique top closing feature that somehow stays open while you access the interior but then also zips in such a way to create additional storage at the top.
It has minimal pockets but that's a plus for me. The only downside is it's 2 pounds, empty. On restrictive airlines the size works but it adds that extra weight to the combined allowance.

This is exactly what you didn't ask for because it hasn't got a lot of pockets meaning its full capacity is better utilized. It will work as a personal item on many airlines. And its $35. I havr used one for close to 15 years. This one.

Mr. E,
You forgot to list your recommended bag. Ooops!

Ooooops......

😱🤣. Quick fix, good rebound.

My husband uses the same bag that Mr. E posted. He likes the zippered pocket at the top for wallet, phone and passport when going through security checkpoints.

misstimetotravel, I second Mustlovedog’s recommendation for the Bagsmart backpack. I have that exact same bag and really like it. It’s exactly as you described in your wishlist. It has lots of pockets that are well placed, a sleeve on the side for a water bottle, and it is shaped like a brick that sits securely on your back and doesn’t protrude.

Honestly, I bought it thinking that I probably wouldn’t like it and was prepared to return it. But after my first trip, I really fell in love with it and now I can’t think of replacing it with anything else. It’s just such a practical bag and it’s very lightweight as well. And I love the clamshell opening, which makes it easier to organize everything.

I just use a cheap Walmart backpack. They are of decent quality and really kind of generic.

Look for a slim, boxy travel backpack with a clamshell opening and a luggage pass through sleeve. Keeping the depth low matters way more than adding pockets.

Cotopaxi all the way.

Jeanm I carry my phone battery, sables and charger there. Then the front zipper has all my papers, confurmatiins, itinerary, etc. And the rear laptop pocket holds the quart bag of liquids cause it's easy to reach if I need to pull them out. I like the bag cause those pockets are thin and dont take away from capacity much.