Narrow Car Seats

I’m trying to avoid purchasing a larger car since I need to buy a small commuter car for work, and I need to make some space in my back seat for a growing step daughter. I know I’ll eventually need to get a bigger car, but both my husband and I commute about an hour in different directions so one of us driving something larger wouldn’t work (CA gas prices like to go up pretty high).

I have twin boys and their car seats take up a lot of space and only leave a small middle section for her to sit and I just want to make more room for her. My boys are almost 2 so this summer I’ll be able to move their car seats to forward facing which would give her room in some areas but take away room on others (our seats are kind of wide on top). However, as much as I want to make room for her to be comfortable, I really don’t want to risk the safety of my boys.

Any recommendations for a safe narrow car seat would truly be appreciated.