I've been using the Kelty Velocity for many years now (based on the name of the pack, it was clearly designed for commuting). I've found it to be great, enough space for either tall work boots and a lunch, or a full set of clothes, jacket and a lunch. It has a large mesh pocket on top made for a helmet or to dry clothes, the essential strap for a blinkie, rain cover and a few reflective areas (see picture with flash lol). I can also carry two water bottles on the sides. Sometimes I wish it had a bit of extra capacity but it probably would make it uncomfortable (maybe, maybe not, who knows).
Unfortunately, they don't make it anymore, or anything equivalent.

But I think that any pack with the same features would be exactly what you need.
Good luck with your search !
J-S