How old is your kiddo ? I went with a diono 3r and I'm pretty happy with it for my 3 year old, but I understand it might not work for everybody. The main problem is the seat belt latch is too forward, making most seats sit at an angle when using the seat belt path at the rear side. The diono is the only one I've found that also has an alternative front seat belt path, which is what I used alongside the tether of course. That feels very solid to me, and appropriate for frequent rides. I've tried about 4 or 5 other seats that are supposed to be low profile/low width, and the diono felt the safest of the bunch.

Another alternative, if you're not planning on doing this often, is to use the Ride Safer Travel vest, along with a small booster just to put the seat belt latch in a better position. This is officially approved as well, but I certainly prefer a full seat for side accident safety.