Henrik C

I recently got an Arc'Teryx Arro 22 as a daypack. I wanted one with fairly little internal organization, but somewhat more than simply one big space - and the kangaroo pocket on the Arro 22 does just that for me. Great for stuffing an extra sweater, jacket etc., especially if they're wet and you'd like to separate them from the rest of your pack.

It's fairly slim with a slightly tapered design, but my 14 inch ThinkPad fits in there. iPads of any size would not be a problem. While it is a 22 liter bag, it doesn't look (nor feel) as big. In large this is due to the kangaroo pocket, as this will collapse on itself and with it empty you're left with only the main compartment. It's a stiff backpack though, so not something you'd stuff in your main bag when not in use.
While the Sea to Summit Ultra-Sil Day Pack (which I also own) is incredibly compact when stuffed, the level of comfort simply isn't there.

The Arro 22 might be on the bigger side for a daypack; mine will be used more for day hikes than around town, so YMMV. Worth a look though.

Dianne47

Brands to consider: Tumi (some on sale now), Tom Bihn, Pacsafe (some models very sleek with excellent security features for when you're in not-so-secure locales). eBags makes several very sleek "professional" backpacks. When I travel with a personal-item-size backpack I use the eBags Weekender Convertible Jr. or an Eddie Bauer model I got at an EB outlet store. Do consider a pack with a sternum strap if you'll be carrying weight all day.

JakiChan

I do like the CoPilot and how it looks...the challenge I'm running in to is that I really would prefer a backpack.

The Port Case that I use (looks like this one) works great, but I find that carrying a satchel/shoulder back around all day to be a challenge - which is why I am looking for a backpack. And the CoPilot isn't a backpack, unless I missed something?

My Verto 26 is a great backpack to pack up small, but it has too little structure. So that's why I'm questing for a small backpack that can carry something like an iPad or a Surface Pro, but nothing bigger, plus my travel carry (camera, earphones, etc). I fear it may not exist. I'm like Goldilocks - that one's too big, that one's too unstructured...

ThomGault

I'll endorse the prior suggestion of Tom Bihn synapse. It's available in either 19 or 25 liter size, is semi-structured, holds all of the items you mentioned, has plenty of organization, and it's very durable.
(The co-pilot referenced is a great bag, too, and can be altered into a loose backpack if you can sew or take and some nylon webbing it to a tailor.)

JakiChan

I'm keeping an eye on it. The color combo I want has been out of stock for a long time.

landscapelover

I use this day pack from Eddie Bauer and love it. Folds into its own front compartment into a small package that I can store in my carry on.

http://www.eddiebauer.com/product/stowaway-packable-20l-daypack/82300168?showProducts=&color=062&sizetype=&size=

k2trvl

I really like the Patagonia lightweight travel tote http://www.patagonia.com/product/lig...&start=1&sz=36, folds nicely into its own pocket.

Kyoto

My favorite day-/backpack, which I am taking since two years or more on every one of my frequent business trips:
https://www.amazon.com/gp/product/B0...A1NUXHOSG6J8RL

I have the 20l and 35l version. The 35l version recently carries 1-2 13" laptops, an ipad, a camera (APS) with ca 3-4 lenses, my liquids, a half liter bottle of water, and a few smaller items. The backpack is sturdy enough, yet extremely lightweight and folds into itself if needed.