My 3 year old (who will be 4 in January) no longer fits in her car seat (5 point harness seat). It is not an infant seat - it is a Britax. We can buckle it across her chest but not in between the legs. The straps do no lengthen anymore. She is too small for a booster seat. What's in between?
We had the Graco Nautilaus, which I loved. But my daughter, 95% on height, 75% on weight, also had issues getting the straps long enough. I am running into that problem with my son who is almost 3. We have an Evenflo Titan for him. I found that they really have to sit up straight and no jackets. That is the only way to be able to buckle.
I have the Graco Nautilaus and second them (Itsacrazylifewith5) and replaced them after a small car accident with the sister to it the Graco Argos. These are 3 - 1 and have high weight limits and steel frame. So 5 point car seat to highback booster to backless booster. My 9 year old 60 lbs just recently went to using it as a highback booster but he could still use it as a car seat. All 3 kids different size and ages use these. For tighter fits, I love the Diono Radian's (Formally Radian Sunshines)
Here you can find out will have a good fit on your car.
Our son will be 4 at the end of December. We moved him from the a britax marathon to the frontier when our daughter needed the marathon. I agree with AV ... Check out the frontier. Great seat. Our little guy can even buckle himself into it ... Though we don't let him unbuckle quite yet.
Britax Frontier 90. 5 pt. harnesd until 90 lbs. and then converts to a booster.
We just moved our 6 yr old to a Frontier because her oldest Marathon expired. I love it. The installation with clicktight (on the 90 model) is amazing. Fitting her in it requires so little effort. Push a button. Pull the headrest. She loves it. I am very very pleased, and it goes from harnessed to booster and lasts 9 years. If you are a Britax family, look into it. Right now they are on sale on Amazon and can ship with Prime. I do not have a big car and it fits perfectly. Even better than the Marathon. Did I mention the install was a breeze? And it is rock solid. That sucker isn't going ANYWHERE. The 90 will also fit your child longer than the Frontier 70 or other models.
In general, I'd be on the lookout for click-tight systems. I'm really impressed.
ETA:
Please double check your state's laws and what the recommendations are. It is a peeve of mine that people are so quick to get their kids out of a seat like it's a big annoyance. Part of the reason small children are supposed to be in a booster is because the seatbelt doesn't hit them right and they are not as safe in an accident. If the child is not 4ft9in tall, then s/he does not meet the critera for not being in a booster. You are doing the right thing for looking for another appropriate seat for her:
http://www.nhtsa.gov/people/injury/childps/archive/promot...
http://www.aap.org/en-us/about-the-aap/aap-press-room/aap...
One reason we chose the Frontier is because she can remain harnessed and it is more than just a lift under her butt when she is yet so small. We have a Bubble Bum for seatbelt fit (for travel), but she doesn't like it. She doesn't feel as secure.
Diono Radian XT - Good for up to 100 lbs, has a 10 year lifespan, and is narrower so up to 3 of them could fit across the typical bench seat.
I have the Graco Nautilaus and agree with Itsacrazylifewith5 and RA.B
Our six year old and 41lbs fits great in it. Plus it was rated one of the top car seats year after year.
My almost 6 year old still fits in a marathon and boulevard... Is your daughter really tall/big? There are tons of larger 5 pt seats, we are using the pinnacle 90 by britax, mine stay in 5 pts until their 7th bday.
Get a Britax Frontier or a Graco Nautilus and it will be the last car seat you ever need. Both convert from a 5 point harness to a high back booster to a backless booster. My son is 7 years old, 60 lbs and about 50" tall, and he can still sit harnessed in both seats.
There are plenty of boosters that harness to a much higher height/weight. I would hazard a guess that you are using a convertible car seat-the stage between infant and booster seat. My 4.5yo dd is currently in a 5pt harness, which converts into a high-back booster when she outgrows the harness. We bought it at a fairly low price at Target, and my DD is far from outgrowing it. She still has at least another year in the harness. She is really tall too- 89% for height, 75% for weight. Unless your dd is a giant, you really shouldn't have any issue finding a harnessed booster to fit.
In Oklahoma a child goes out of a carseat completely the day they turn 6. SO our kids were already in boosters when they were 3. The booster sits the child up high enough so the seat belt fits across them at the right point. If you wanted to do a booster with a back on it the top has a slot for the seat belt to go through to make sure the seat belt goes across the chest.
To me the seat belt is more dependable than a plastic car seat.
