I have been using Graco extend2fit for my kid. They come with isofix latch system which is a lot more convenient vs the rigid isofix base system in some car seats. The good thing with this carseat is that you can also use it with seatbelt both for rear and forward facing. Can use from infant like I have been using for my kids. currently my 4 y/o are sitting in it.

My advice is buy this kind of car seat with latch isofix system as its normally can also be used with a seatbelt. And in case you upgrade your car with an isofix in the future you can also use the isofix function. And the installation using isofix latch is much2 more easier IMO vs the isofix base system based on my personal experience.

Im not sure if the model is still available tho. bought mine 8 years ago. But graco line is using this system. you can also check Chicco, the also use similar system. But the seat is heavier as compared to Graco so I would give my pick to Graco

Unless you child seat you are going to buy have a top tether It's quite difficult to get a snug & tight fit. This differs car by car basis. The car seat branc that I recommended have top tether so you can also use whichever more convenient