Booster Seat for Older Car

According to this site there are no booster seats that will work with just a lap belt:

http://www.cpsafety.com/articles/boosterbasics.aspx

Significant risk of head and neck injuries without the use of a shoulder belt in conjunction with a lap belt.

You might look into something like a Britax Frontier 85 that will keep her in a 5 pt harness up to 85lbs. But check their site and measure her sitting height to see how long she might be able to use the seat.

Just found this site that gives some options for cars that only have lap belts:

http://www.healthychildren.org/English/safety-prevention/...

None of them sound like great options though.

Nope, there are no belt only booster seats that only use the lap belt, and its incredibly dangerous to use the lap belt only with or without a booster seat. Google SEATBELT SYNDROME!

What you need to look for is a higher harness weight seat like the Graco Nautilus or Britax Frontier. Or look for the 86Y harness(works with a booster), or the safe Rider travel vest. that works with lap only belts that provides proper protection.

She cannot CANNOT sit in the lap belt only with or without a booster. She needs a harnessed car seat or the 86Y vest!

The only booster type restraints I know of that can work with a lap belt are the RideSafer Travel Vest (which requires the use of a top tether anchor if used with just a lap belt http://www.ridesafer.net ), the discontinued Britax Laptop, and the EZ-On vests http://www.ezonpro.com/products/familyVehicle.shtml . I'm not sure if your mom's car comes with a top tether anchor or could be retrofitted with one - this would be a great question to ask the many certified child-passenger safety technicians (CPST's) at http://www.car-seat.org . I have a RideSafer vest that I use with lap belt and top tether in the rear-center seat of my 1997 Honda Civic and while it's a little more work than a belt-positioning booster, it has excellent safety ratings and is very portable and narrow (allows me to safely transport 3 kids in the back of my Civic for carpool b/c it's narrow enough to fit between the two belt-positioning boosters in the rear outboard seats)

What is your 5YO's weight and torso height (sit her criss-cross applesauce with her back to the wall and measure the distance from floor to her shoulder)?
Your most affordable option, if she fits it, would be the Evenflo Maestro which is a forward facing "combination" seat that can be used with harness to 50 lbs. or about 18" of torso height, then can be used as a booster when the harness is outgrown.

I remember the booster seat my brothers and I used when we were little only required the lap belt, but that was a long time ago. I've seen boosters that REMIND me of that one. The one I just found is an Evenflo No Back booster seat. I don't see anything on it about what requirements there are seatbelt-wise, but I'm sure you could find any of the "No Back" boosters at a Wal-Mart or Target nearby (or the website Dori W. listed) and find out more info to know for sure.

I don't think you can use ANY booster seat with only a lap belt. Very dangerous. I think the only other choice is to buy a seat with a 5 pt harness that will accommodate a larger child.

The others are right, you would need either one of the vests or a seat with a harness....there are lots of them now that go up to 65 lbs or even 80 lbs that would work for a 5 year old. You might also check and see if your Mom could have her car retrofitted for a shoulder belt. That would probably be more expensive but safer.