Convertible seat for Babysitter's Car

[Sayla27]

I'm hoping all you "experts" out there can help me (especially Jools!) I need to get a car seat for my babysitter's car, but I don't want to spend a ton of $$ since she will only be watching her for about six months. My daughter is 18mo and 22 lbs. Most trips will be less than ten miles (library visits mainly). I don't mind investing a bit since I would also use this seat if we travel on a plane since the Britax Marathon is simply too big. Any help would be appreciated.

[Joolsplus2]

Roundabout 50? It's a lot like the Marathon, but actually a LOT lighter since it's lacking the LATCH bars and lockoffs :).
But something small like the Scenera or Titan or Tribute are also good for younger kids, light, not toooo hard to install (not as easy as the Marathon or RA 50, though), and light for travel :)