From what you mention, you say lightweight to medium size but mention the smallest - ultra-compact strollers. Those two in the category are a good choice, even though only one is a reversible-seat stroller.
Usually, the more upright strollers are the larger ones - e.g., the Joie Versatrax/Joie Finiti which are not super small but would work from the compact and upright point of view. These are the ones I would even suggest.
The Tuc Tuc Kimbo is also a new stroller that sports an upright seat, but it is not available everywhere.
Lastly, again, do count on a reversible seater to be BIGGER than a lightweight model. And if you need a lightweight model, the Cybex Eezy S-Twist 2 Plus would be your go-to, if the reversibility is your priority.