I have a Thule Subterra 23l. It is a great size for just toting a laptop and maybe a small lunch bag. It is not overly bulky at all and is very clean in style, very professional in my opinion.

Additionally, you can find it on Amazon ;)

https://www.amazon.com/Thule-Subterra-3203438-Backpack-Mineral/dp/B01MRXF63T?source=ps-sl-shoppingads-lpcontext&ref\_=fplfs&psc=1&smid=ATVPDKIKX0DER