As the subject says I'm looking for a personal-item (underseat) sized backpack where I can tuck the straps into the back, that has a trolley sleeve/strap, a bottle holder, and a front (i.e. easily accessible) organizer pocket for passport, pen, phone, etc.

The Osprey Daylite Carry-On Travel Pack 35 has all the features I'm looking for, but at 19.3 x 14.6 x 10.2 and a stiff back panel, it can't be squeezed into an 18x14x8 sizer.